WO2023218948A1 - Silica particle dispersion liquid - Google Patents

Silica particle dispersion liquid Download PDF

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Publication number
WO2023218948A1
WO2023218948A1 PCT/JP2023/016363 JP2023016363W WO2023218948A1 WO 2023218948 A1 WO2023218948 A1 WO 2023218948A1 JP 2023016363 W JP2023016363 W JP 2023016363W WO 2023218948 A1 WO2023218948 A1 WO 2023218948A1
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Prior art keywords
silica
silica particles
hollow silica
particles
particle dispersion
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PCT/JP2023/016363
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French (fr)
Japanese (ja)
Inventor
博道 加茂
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Ａｇｃ株式会社
Ａｇｃエスアイテック株式会社
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Publication of WO2023218948A1 publication Critical patent/WO2023218948A1/en

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/14—Colloidal silica, e.g. dispersions, gels, sols
    • C01B33/145—Preparation of hydroorganosols, organosols or dispersions in an organic medium
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/34—Silicon-containing compounds
    • C08K3/36—Silica
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K7/00—Use of ingredients characterised by shape
    • C08K7/22—Expanded, porous or hollow particles
    • C08K7/24—Expanded, porous or hollow particles inorganic
    • C08K7/26—Silicon- containing compounds

Definitions

  • the present invention relates to a silica particle dispersion in which silica particles are dispersed in a solvent.
  • Silica particles have traditionally been used in a variety of applications, including electronic materials such as printed wiring boards and package wiring boards, optical materials such as lenses and optical films, functional materials such as catalysts and catalyst carriers, and pigments for paints and cosmetics. ing. Among them, hollow silica particles have characteristics such as low refractive index, low dielectric constant, and low density, so they are suitable for resin compositions used in insulating resin sheets such as adhesive films, prepregs, and insulating layers formed on printed wiring boards. It is used to lower the dielectric constant, dielectric loss tangent, and thermal expansion of materials.
  • Silica particles tend to aggregate when used in the dry powder state, so depending on the purpose of use, they are used in the form of a dispersion in a solvent such as water or resin.
  • a solvent such as water or resin.
  • Patent Document 1 states that the particle size is 100 nm to 2000 nm or the specific surface area is 2 m 2 /g to 35 m 2 /g, and the amount of water generated when heated at 200°C is 40 ppm per 1 m 2 of surface area.
  • a filler for electronic materials which is a silica particle material whose surface is treated with a silane compound having a vinyl group, a phenyl group, a phenylamino group, an alkyl group having 4 or more carbon atoms, a methacrylic group, or an epoxy group;
  • a slurry for electronic materials including a liquid dispersion medium that does not substantially contain water has been proposed.
  • Patent Document 2 describes silica-based hollow fine particles (A) having an average particle diameter (Dpa) in the range of 30 to 200 nm, and silica solid fine particles (B) having an average particle diameter (Dpb) in the range of 5 to 80 nm.
  • concentration (CA) of the silica-based hollow particles (A) is in the range of 0.2 to 8% by weight as a solid content
  • concentration (CB) of the silica solid particles (B) is 0.2 to 8% by weight as a solid content.
  • a coating liquid for forming an anti-reflection film having a weight ratio (B/A) of silica-based hollow fine particles (A) to silica solid fine particles (B) of 0.25 to 4, which is in the range of 2 to 8% by weight. is proposed.
  • Patent Document 3 describes silica-based particles having an average particle diameter of 5 to 40 nm and a ratio of the number of hollow particles to the total number of hollow particles and solid particles (hollowness ratio) of 70% or more. Dispersions of silica-based particles have been proposed.
  • silica particle dispersions when conventional silica particle dispersions are incorporated into a resin composition and formed into a film, the silica particles tend to clump, resulting in low peel strength, and it is sometimes difficult to obtain the expected effects of silica particles. Ta.
  • the present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a silica particle dispersion liquid that can suppress grain formation during film formation and increase peel strength.
  • the present invention relates to the following (1) to (11).
  • the hollow silica particles described in (1) or (2) above have a particle density of 2.00 to 2.30 g/cm 3 as determined by density measurement with a dry pycnometer using helium gas. silica particle dispersion.
  • the above (1) further contains a silane compound having at least one group selected from the group consisting of a vinyl group, a phenyl group, a phenylamino group, an alkyl group having 4 or more carbon atoms, a methacrylic group, and an epoxy group.
  • the solvent includes at least one selected from the group consisting of water, hydrocarbons, alcohols, acetate esters, ketones, cellosolves, glycol ethers, chlorinated hydrocarbons, and polar solvents.
  • (10) A resin composition containing the silica particle dispersion according to any one of (1) to (9) above.
  • silica particle dispersion of the present invention hollow silica particles are uniformly dispersed in the liquid without agglomeration, so grain formation is suppressed when a resin composition containing the silica particle dispersion of the present invention is formed into a film. It also increases the peel strength.
  • the silica particle dispersion of the present invention contains hollow silica particles and a solvent, and the hollow silica particles have an average particle diameter in the range of 0.2 to 10 ⁇ m.
  • the hollow silica particles are uniformly dispersed without agglomeration, and the dispersion stability of the hollow silica particles in the dispersion is improved. It is possible to suppress grain formation during peeling and increase peel strength.
  • the solvent used as the dispersion medium for the silica particle dispersion can be arbitrarily selected depending on the purpose of use, and examples include water, hydrocarbons, alcohols, acetate esters, ketones, cellosolves, glycol ethers, and chlorinated hydrocarbons. and polar solvents.
  • the solvent contains at least one selected from the group consisting of these.
  • hydrocarbons examples include toluene, methylcyclohexane, normal heptane, m-xylene, and the like.
  • alcohols include ethanol, isopropyl alcohol, 1-propyl alcohol, isobutyl alcohol, 1-butanol, 2-butanol, and the like.
  • acetic acid esters include propyl acetate, isobutyl acetate, butyl acetate, and the like.
  • ketones examples include methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone.
  • cellosolves include ethylene glycol monomethyl ether and ethylene glycol monoethyl ether.
  • glycol ethers examples include 1-methoxy-2-propanol, 1-methoxypropyl-2-acetate, 1-ethoxy-2-propanol, and ethyl 3-ethoxypropionate.
  • chlorinated hydrocarbons examples include trichlorethylene and tetrachloroethylene.
  • the polar solvent examples include N-methyl-2-pyrrolidone.
  • the solvent may be appropriately selected depending on the intended field of use.
  • ketones and hydrocarbons it is preferable to use ketones and hydrocarbons, and specifically, it is preferable to use methyl ethyl ketone (MEK), toluene, etc.
  • MEK methyl ethyl ketone
  • the liquid main ingredient or curing agent itself may be used as a solvent.
  • the base resin include epoxy resins, polyphenylene ether resins, polyester resins, polyimide resins, phenol resins, ortho-divinylbenzene resins
  • the curing agent include polyamine-based curing agents and acid anhydride-based curing agents. , phenolic curing agents, active ester curing agents, peroxides, and the like.
  • the solvent is preferably contained in the silica particle dispersion in a range of 20 to 90% by volume.
  • the content of the solvent is 20% by volume or more, the hollow silica particles can be uniformly dispersed, and the viscosity of the dispersion liquid does not become too high, making it easy to handle.
  • the content of the solvent is 90% by volume or less, it is liquid and can be used in a dispersed state.
  • the content of the solvent in the silica particle dispersion is more preferably 25% by volume or more, even more preferably 30% by volume or more, more preferably 80% by volume or less, and even more preferably 70% by volume or less. It is preferably at most 60% by volume, particularly preferably at most 50% by volume.
  • Hollow silica particles are silica particles that include a shell layer (solid film) containing silica and have a space inside the shell layer.
  • the fact that the hollow silica particles have a space inside the shell layer can be confirmed by transmission electron microscopy (TEM) observation or scanning electron microscopy (SEM) observation. In the case of SEM observation, it can be confirmed that the particle is hollow by observing a partially opened broken particle.
  • TEM transmission electron microscopy
  • SEM scanning electron microscopy
  • the physical properties of the hollow silica particles described below can be confirmed by drying a silica particle dispersion to obtain powdery silica particles.
  • the shell layer "contains silica” means that it contains 50% by mass or more of silica (SiO 2 ).
  • the composition of the shell layer can be measured by ICP emission spectrometry, flame atomic absorption spectrometry, or the like.
  • the shell layer contains preferably 80% by mass or more of silica, more preferably 95% by mass or more. The upper limit is theoretically 100% by mass.
  • the silica contained in the shell layer is preferably less than 100% by mass, more preferably 99.99% by mass or less.
  • Residues include alkali metal oxides and silicates, alkaline earth metal oxides and silicates, carbon, and the like.
  • "having a space inside the shell layer” means a hollow state in which the shell layer surrounds one space when the cross section of one primary particle is observed. That is, one hollow particle has one large space and a shell layer surrounding it.
  • the composition containing the silica particle dispersion of the present invention can secure more space in the composition, making it suitable for use in insulating layers of electronic devices, etc. When this happens, the dielectric constant can be lowered.
  • the average particle diameter (D50, median diameter) of the hollow silica particles dispersed in the silica particle dispersion of the present invention is 0.2 to 10 ⁇ m. Note that in hollow silica particles, primary particles are partially bonded to each other during the firing and drying steps during production, so hollow silica particles are often an aggregate of secondary particles in which primary particles are aggregated.
  • the average particle diameter of hollow silica particles herein refers to the particle diameter of secondary particles, and primary particles refer to spherical particles with internal spaces that can be confirmed by TEM observation or SEM observation.
  • the average particle diameter (D50) of the hollow silica particles in the silica particle dispersion is in the range of 0.2 to 10 ⁇ m, the silica particle dispersion has a viscosity that is easy to handle, and it is difficult to form particles during coating, so the resin composition When used as a product, the peel strength of the resin composition is maintained appropriately.
  • the average particle diameter (D50) is preferably 0.5 ⁇ m or more, more preferably 1 ⁇ m or more, and preferably 8 ⁇ m or less, more preferably 6 ⁇ m or less, and even more preferably 5 ⁇ m or less.
  • the average particle diameter (particle diameter of secondary particles) of hollow silica particles is preferably measured by laser scattering. This is because measuring the agglomerate diameter by SEM does not reflect the dispersion in a wet state because the boundaries between particles are unclear. In addition, in measurements using a Coulter counter, the electric field changes differ between hollow particles and solid particles, making it difficult to obtain values corresponding to solid particles.
  • the coarse particle diameter (D90) of the secondary particles of the hollow silica particles is preferably 1 to 30 ⁇ m. From the viewpoint of production efficiency, the coarse particle size is preferably 1 ⁇ m or more. Further, if the coarse particle size is too large, it will cause graininess when the resin composition is molded into a film, so it is preferably 30 ⁇ m or less.
  • the lower limit of the coarse particle size is more preferably 3 ⁇ m or more, most preferably 5 ⁇ m or more, and the upper limit is preferably 30 ⁇ m or less, more preferably 25 ⁇ m or less, even more preferably 20 ⁇ m or less, and most preferably 15 ⁇ m or less. .
  • the coarse particle size is also determined by measuring the particle size of secondary particles by laser scattering.
  • the size of the primary particles of hollow silica particles can be determined by directly observing the particle size (diameter) using SEM observation, and the average value of the size of the primary particles (average primary particle size) is 50 nm to 10 ⁇ m. It is preferable that it is in the range of .
  • the average primary particle diameter is 50 nm or more, increases in specific surface area, oil absorption, and pore volume can be suppressed, and increases in the amount of SiOH and adsorbed water on the particle surface can be suppressed, making it difficult for the dielectric loss tangent to increase.
  • the average primary particle diameter is 10 ⁇ m or less, it is easy to handle as a filler. From the viewpoint of manufacturing reproducibility, the average primary particle diameter has a lower limit of preferably 70 nm or more, even more preferably 100 nm or more, and an upper limit of 5 ⁇ m or less, particularly preferably 3 ⁇ m or less.
  • the average primary particle diameter of hollow silica particles is determined by measuring the primary particle size of 100 particles from a SEM image, and calculating the distribution of the primary particle size obtained by aggregating them. is estimated to be the size distribution of the primary particles.
  • the primary particle diameter of particles that are difficult to deagglomerate can be directly measured.
  • the hollow silica particles of the present invention have the above-described average primary particle diameter, and it is preferable that 40% or more of the entire particles have a particle diameter within ⁇ 40% of the average primary particle diameter.
  • the particle diameter of 40% or more of the particles is within ⁇ 40% of the average primary particle diameter, the size of the hollow silica particles becomes uniform, and shell defects of the hollow silica particles are less likely to occur.
  • 50% or more of the entire particles have an average primary particle diameter within ⁇ 40%, even more preferably that 60% or more of the entire particles have an average primary particle diameter within ⁇ 40%, and 70% or more of the entire particles is particularly preferably within ⁇ 40% of the average primary particle diameter.
  • the hollow silica particles preferably have a particle density (hereinafter also referred to as Ar density) of 0.35 to 2.00 g/cm 3 as determined by density measurement using a dry pycnometer using argon gas.
  • Ar density particle density
  • the Ar density is 0.35 g/ cm3 or more, cracking of particles in the dispersion can be suppressed, and the difference in specific gravity with the resin will not become too large, so when the silica particle dispersion is mixed with the resin, Dispersibility in the resin composition can be improved.
  • the Ar density is 2.00 g/cm 3 or less, the effect of reducing the dielectric constant is easily exhibited, so that it can be preferably used as a material for electronic devices.
  • the Ar density is more preferably 0.40 g/cm 3 or more, and the upper limit is more preferably 1.50 g/cm 3 or less, even more preferably 1.00 g/cm 3 or less. According to Guda, the Ar density is more preferably 0.35 to 1.50 g/cm 3 , even more preferably 0.40 to 1.00 g/cm 3 .
  • the hollow silica particles preferably have a particle density (hereinafter also referred to as He density) of 2.00 to 2.30 g/cm 3 as determined by density measurement using a dry pycnometer using helium gas. Since helium gas permeates through minute voids, a density corresponding to the true density of the silica portion of the silica particles having spaces inside can be obtained.
  • He density is 2.00 g/cm 3 or more
  • the silica particles are dense, so when the silica particle dispersion is mixed with a resin and used, the peel strength of the resin composition will not be reduced, and Since the residual amount of silanol contained in the hollow silica particles is reduced, it is easy to lower the dielectric loss tangent.
  • the He density is more preferably 2.05 g/cm 3 or more, even more preferably 2.10 g/cm 3 or more, and more preferably 2.25 g/cm 3 or less, 2.23 g/cm 3 or more. More preferably, it is 3 or less.
  • the He density is more preferably 2.05 to 2.25 g/cm 3 , even more preferably 2.10 to 2.23 g/cm 3 .
  • the apparent density of hollow silica particles can also be measured using a pycnometer. Put a sample (hollow silica particles) and an organic solvent into a pycnometer, and measure after standing at 25°C for 48 hours. Since it may take some time for the organic solvent to permeate depending on the density of the shell of the hollow silica particles, it is preferable to leave it for the above-mentioned period of time.
  • the results measured by this method correspond to the results of density measurements using a dry pycnometer using argon gas.
  • the apparent density of hollow silica particles can be adjusted by adjusting the primary particle diameter and shell thickness, and by changing the density of the particles, it is possible to determine whether they will settle in the solvent, continue to disperse, or float to the top. Can be adjusted.
  • dispersing particles in a solvent it is desirable that the density of the solvent and the apparent density of the particles be close to each other. For example, when dispersing particles in water with a density of 1.0 g/cm 3 , it is preferable to adjust the apparent density of the particles to 0.8 g/cm 3 or more and 1.2 g/cm 3 or less.
  • the hollow silica particles preferably have a BET specific surface area of 1 to 100 m 2 /g. It is substantially difficult to reduce the BET specific surface area to less than 1 m 2 /g. In addition, if the BET specific surface area is too large, more resin etc. will be adsorbed on the silica surface, but if the BET specific surface area is 100 m 2 /g or less, the amount of adsorption of resin etc. will be suppressed, and when used as a resin composition. viscosity increase can be suppressed.
  • the BET specific surface area is preferably 1 to 100 m 2 /g, more preferably 1 to 50 m 2 /g, even more preferably 1 to 20 m 2 /g, and most preferably 1 to 15 m 2 /g.
  • the BET specific surface area is measured using a specific surface area measuring device (for example, "Tristar II 3020" manufactured by Shimadzu Corporation), after drying the hollow silica particles at 230 ° C. until the pressure becomes 50 mTorr as a pretreatment.
  • a specific surface area measuring device for example, "Tristar II 3020” manufactured by Shimadzu Corporation
  • Hollow silica particles have Ar density and BET specific surface area (A x B) of 1 to 120 m 2 when Ar density is A (g/cm 3 ) and BET specific surface area is B (m 2 /g). /cm 3 is preferred.
  • a ⁇ B indicates the specific surface area per volume when hollow silica particles are dispersed in a solvent. For example, when added to a resin, the specific surface area of the portion occupied by the hollow silica particles in a given volume of the resin is show. Since the hollow silica particles satisfy the above relationship between Ar density and BET specific surface area, when a resin composition containing the hollow silica particles is used for the insulating layer, the dielectric constant of the insulating layer is lowered and the dielectric loss is reduced.
  • a ⁇ B is preferably 80 m 2 /cm 3 or less, more preferably 40 m 2 /cm 3 or less, and even more preferably 20 m 2 /cm 3 or less.
  • a ⁇ B is preferably 2 m 2 /cm 3 or more, more preferably 2.5 m 2 /cm 3 or more, and even more preferably 3 m 2 /cm 3 or more.
  • the hollow silica particles preferably have a sphericity of 0.75 to 1.0. If the sphericity becomes too low, the contact area of the silica particles in the resin layer with the member in contact with the resin composition containing the silica particle dispersion may decrease, resulting in a decrease in peel strength. is preferably 0.75 or more.
  • Sphericity is defined as the maximum diameter (DL) of any 100 particles in a photographic projection obtained by photographing with a scanning electron microscope (SEM), and the minimum diameter (DS) orthogonal to this. is measured, and the ratio of the minimum diameter (DS) to the maximum diameter (DL) (DS/DL) is expressed as the calculated average value.
  • the sphericity is more preferably 0.80 or more, even more preferably 0.82 or more, even more preferably 0.83 or more, particularly preferably 0.85 or more, and 0.80 or more.
  • a value of 87 or more is particularly preferred, and a value of 0.90 or more is most preferred.
  • the shell thickness of the hollow silica particles is preferably 0.01 to 0.3 per diameter 1 of the primary particles.
  • the shell thickness is more preferably 0.02 or more, even more preferably 0.03 or more, and more preferably 0.2 or less, and 0.1 or less with respect to the diameter 1 of the primary particle. More preferred.
  • the shell thickness is determined by measuring the shell thickness of each particle using a transmission electron microscope (TEM).
  • TEM transmission electron microscope
  • hollow silica particles have a space inside, they can contain substances inside the particles. Since the hollow silica particles of the present invention have a dense shell layer, it is difficult for various solvents to penetrate into them, but if there are damaged particles, the solvent will penetrate inside. Therefore, the oil absorption amount changes depending on the proportion of damaged particles.
  • the oil absorption amount of the hollow silica particles is preferably 15 to 1300 mL/100 g.
  • the oil absorption amount is 15 mL/100 g or more, adhesion with the resin can be ensured when used in a resin composition, and when it is 1300 mL/100 g or less, the strength of the resin can be ensured when used in a resin composition.
  • the oil absorption amount can be adjusted by adjusting the proportion of damaged particles. Furthermore, since the space between primary particles is also a space that can hold oil, the larger the median diameter of the secondary particles that are agglomerated primary particles, the greater the oil absorption, and the smaller the median diameter of the secondary particles, the greater the oil absorption. It is possible that it will decrease.
  • the hollow silica particles preferably contain one or more metals M selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, and Ba.
  • metal M selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, and Ba.
  • the inclusion of metal M in the hollow silica particles acts as a flux during firing, reduces the specific surface area, and lowers the dielectric loss tangent.
  • Metal M is contained between the reaction step and the washing step in the production of hollow silica particles.
  • a metal salt of the metal M may be added to the reaction solution when forming a silica shell, or a solution containing metal ions of the metal M may be added before baking the hollow silica precursor. By washing, the metal M can be contained in the hollow silica particles.
  • the concentration of metal M contained in the hollow silica particles is preferably 50 mass ppm or more and 1 mass % or less.
  • the concentration of metal M is more preferably 100 mass ppm or more, more preferably 150 ppm or more, and preferably 1 mass % or less, preferably 5000 mass ppm or less, and most preferably 1000 mass ppm or less.
  • Metal M can be measured by ICP emission spectrometry after adding perchloric acid and hydrofluoric acid to hollow silica particles and igniting them to remove the main component, silicon. Furthermore, when an alkali metal silicate is used as the silica raw material, the carbon (C) component derived from the raw material is reduced in the shell layer of the resulting hollow silica particles, compared to when a silicon alkoxide is used as the silica raw material.
  • the hollow silica particles preferably have a viscosity of 20,000 mPa ⁇ s or less when the following kneaded product containing the hollow silica particles is measured by the following measuring method.
  • Measurement method Mix 6 parts by mass of boiled linseed oil and 6 parts by mass of hollow silica particles (6 ⁇ A/2.2), assuming the particle density determined by density measurement with a dry pycnometer using argon gas as A (g/cm 3 ).
  • the kneaded product obtained by kneading at 2000 rpm for 3 minutes was measured for 30 seconds at a shear rate of 1 s -1 using a rotary rheometer, and the viscosity at the 30 second time point was determined.
  • the viscosity of the kneaded product at a shear rate of 1 s ⁇ 1 determined by the above measurement method is 20,000 mPa ⁇ s or less, the amount of solvent added during molding and film formation of the resin composition containing hollow silica particles can be reduced, and the drying rate can be increased. It can be done quickly and productivity can be improved.
  • the viscosity tends to increase when added to a resin composition, but hollow silica particles have a small product of density and specific surface area. Increase in viscosity of the resin composition can be suppressed.
  • the viscosity of the kneaded material is more preferably 8000 mPa ⁇ s or less, even more preferably 5000 mPa ⁇ s or less, and most preferably 4000 mPa ⁇ s or less.
  • the lower limit of the viscosity of the kneaded product at a shear rate of 1 s -1 is not particularly limited because the lower the viscosity, the better the coating properties of the resin composition and the higher the productivity.
  • Silica particles are classified into four basic structures represented by Q1 to Q4 according to the degree of connection of SiO 4 tetrahedra in the spectrum assignment by 29 Si-NMR.
  • Q1 to Q4 are each as follows.
  • Q1 is a structural unit that has one Si around Si via oxygen, and a SiO 4 tetrahedron is connected to another SiO 4 tetrahedron, resulting in a solid 29 Si-DD/MAS-NMR
  • the spectrum has a peak around -80 ppm.
  • Q2 is a structural unit that has two Si around Si via oxygen, and a SiO 4 tetrahedron is connected to two other SiO 4 tetrahedra, resulting in a solid 29 Si-DD/MAS-NMR
  • the spectrum has a peak near -91 ppm.
  • Q3 is a structural unit that has three Si atoms around Si via oxygen, and a SiO 4 tetrahedron is connected to three other SiO 4 tetrahedra, resulting in a solid 29 Si-DD/MAS-NMR
  • the spectrum has a peak around -101 ppm.
  • Q4 is a structural unit that has four Si atoms around Si through oxygen, and the SiO 4 tetrahedron is connected to other 4 SiO 4 tetrahedra, resulting in solid 29 Si-DD/MAS-NMR.
  • the spectrum has a peak near -110 ppm.
  • the hollow silica particles of the present invention have a molar ratio (Q3 /Q4) is preferably 2 to 40%.
  • Q3/Q4 is 40% or less, the amount of silanol can be suppressed and the dielectric loss tangent is improved. It is substantially difficult to obtain a material with Q3/Q4 of less than 2% because it requires firing at a high temperature and the hollow portion of the hollow silica shrinks during this process. Further, Q3/Q4 is more preferably 30% or less, and even more preferably 20% or less.
  • Q3/Q4 of hollow silica particles is measured as follows.
  • a hollow silica particle powder is used as a measurement sample.
  • a CPSAS probe with a diameter of 7.5 mm is attached, the observation nucleus is 29 Si, and measurements are performed using the DD/MAS method.
  • the measurement conditions were: 29 Si resonance frequency of 79.43 MHz, 29 Si 90° pulse width of 5 ⁇ s, 1H resonance frequency of 399.84 MHz, 1H decoupling frequency of 50 kHz, MAS rotation speed of 4 kHz, spectral width of 30.49 kHz,
  • the measurement temperature is 23°C.
  • optimization calculations are performed using the nonlinear least squares method for each peak in the spectrum after Fourier transformation, using the center position, height, and half-width of the peak shape created by mixing the Lorentz waveform and Gaussian waveform as variable parameters. .
  • Targeting the four structural units Q1, Q2, Q3 and Q4, the molar ratio of Q3 and Q4 is calculated from the obtained content of Q1, content of Q2, content of Q3 and content of Q4.
  • the content of silanol groups in the silica particles is measured not by the CPSAS method (Cross Polarization/Magic Angle Spinning) but by the DD/MAS method (Dipolar Decoupling/Magic Angle Spinning).
  • CPSAS method Cross Polarization/Magic Angle Spinning
  • DD/MAS method Dipolar Decoupling/Magic Angle Spinning
  • 1 H sensitizes and detects Si present in the vicinity, so the obtained peaks accurately reflect the content of Q1, Q2, Q3, and Q4. do not.
  • the DD/MAS method does not have a sensitizing effect like the CPSAS method, so the obtained peaks accurately reflect the content of Q1, Q2, Q3, and Q4, and can be quantified. Suitable for analytical analysis.
  • the pore volume of the hollow silica particles is preferably 0.2 cm 3 /g or less.
  • the pore volume is more preferably 0.15 cm 3 /g or less, even more preferably 0.1 cm 3 /g or less, and particularly preferably 0.05 cm 3 /g or less.
  • the surface of the hollow silica particles may be treated with a silane coupling agent. Since the surface of the hollow silica particles is treated with a silane coupling agent, the amount of remaining surface silanol groups is reduced, the surface is made hydrophobic, and water adsorption can be suppressed and dielectric loss improved, and the resin composition and When doing so, the affinity with the resin is improved, and the dispersibility and strength after resin film formation are improved.
  • wet treatment conditions There are no particular restrictions on the surface treatment conditions, and general surface treatment conditions may be used, and wet treatment methods and dry treatment methods may be used. From the viewpoint of uniform treatment, a wet treatment method is preferred.
  • silane coupling agents include aminosilane coupling agents, epoxysilane coupling agents, mercaptosilane coupling agents, silane coupling agents, organosilazane compounds, and the like.
  • One type of silane coupling agent may be used alone, or two or more types may be used in combination.
  • examples of the silane coupling agent include aminopropylmethoxysilane, aminopropyltriethoxysilane, ureidopropyltriethoxysilane, N-phenylaminopropyltrimethoxysilane, N-2 (aminoethyl)aminopropyltrimethoxysilane, etc.
  • Aminosilane coupling agent glycidoxypropyltrimethoxysilane, glycidoxypropyltriethoxysilane, glycidoxypropylmethyldiethoxysilane, glycidylbutyltrimethoxysilane, (3,4-epoxycyclohexyl)ethyltrimethoxysilane
  • Epoxysilane coupling agents such as mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane; methyltrimethoxysilane, vinyltrimethoxysilane, octadecyltrimethoxysilane, phenyltrimethoxysilane, meth Silane coupling agents such as chloropropyltrimethoxysilane, imidazolesilane , triazinesilane ; CF3 ( CF2 ) 7CH2CH2Si ( OCH3 ) 3 , CF3
  • the amount of the silane coupling agent attached is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, even more preferably 2 parts by mass or more, based on 100 parts by mass of the hollow silica particles. Moreover, it is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less.
  • the surface of the hollow silica particles has been treated with the silane coupling agent by detecting a peak due to the substituent of the silane coupling agent using IR. Further, the amount of attached silane coupling agent can be measured by the amount of carbon.
  • the hollow silica particles preferably have a dielectric constant of 1.3 to 5.0 at 1 GHz. Particularly in the measurement of the dielectric constant of powder, at frequencies above 10 GHz, the sample space becomes small and the measurement accuracy deteriorates, so in the present invention, measured values at 1 GHz are used. When the dielectric constant at 1 GHz is within the above range, a low dielectric constant required for electronic devices can be achieved. Note that it is substantially difficult to synthesize hollow silica particles having a dielectric constant of less than 1.3 at 1 GHz.
  • the lower limit of the dielectric constant at 1 GHz is preferably 1.3 or more, more preferably 1.4 or more. Further, the upper limit is more preferably 4.5 or less, even more preferably 4.0 or less, even more preferably 3.5 or less, particularly preferably 3.0 or less, and most preferably 2.5 or less.
  • the hollow silica particles preferably have a dielectric loss tangent of 0.0001 to 0.05 at 1 GHz.
  • the dielectric loss tangent at 1 GHz is 0.05 or less, a low dielectric constant required for electronic devices can be achieved. Further, it is substantially difficult to synthesize hollow silica particles having a dielectric loss tangent of less than 0.0001 at 1 GHz.
  • the lower limit of the dielectric loss tangent at 1 GHz is more preferably 0.0002 or more, and even more preferably 0.0003 or more.
  • the upper limit is more preferably 0.01 or less, further preferably 0.005 or less, even more preferably 0.003 or less, particularly preferably 0.002 or less, particularly preferably 0.0015 or less, and even more preferably 0.0015 or less. 0010 or less is most preferable.
  • the relative permittivity and dielectric loss tangent can be measured using a perturbation resonator method using a dedicated device (for example, "Vector Network Analyzer E5063A” manufactured by Keycom Co., Ltd.).
  • the hollow silica particles are preferably contained in the silica particle dispersion in a range of 5 to 80% by volume.
  • the content of hollow silica particles is 5% by volume or more, the desired peel strength can be imparted with a small amount of silica particle dispersion added to the resin composition, and when the content is 80% by volume or less, the viscosity of the dispersion is low. It does not rise too much and is easy to handle.
  • the content of hollow silica particles in the silica particle dispersion is more preferably 10% by volume or more, even more preferably 20% by volume or more, and more preferably 70% by volume or less, and 60% by volume or less. It is more preferable, and particularly preferably 50% by volume or less.
  • silica particle dispersion of the present invention contains a silane compound having at least one group selected from the group consisting of vinyl group, phenyl group, phenylamino group, alkyl group having 4 or more carbon atoms, methacrylic group, and epoxy group. It is preferable to do so.
  • a silane compound having at least one group selected from the group consisting of vinyl group, phenyl group, phenylamino group, alkyl group having 4 or more carbon atoms, methacrylic group, and epoxy group. It is preferable to do so.
  • the silane compound when the silica particle dispersion is included in the resin composition, the surface of the hollow silica particles blends into the resin, so that the peel strength of the resin composition can be further increased. Note that when the hollow silica particles are treated with a silane coupling agent, it is not necessarily necessary to add a silane compound.
  • silane compound examples include vinylsilane, phenylsilane, phenylaminosilane, hexylsilane, decylsilane, 3-methacryloxypropyltrimethoxysilane, and aminopropylsilane. These may be used alone or in combination of two or more. Among these, from the viewpoint of interaction with the resin, silane compounds containing a vinyl group, phenyl group, methacrylic group, epoxy group or phenylamino group are preferable, and silane compounds containing a vinyl group, phenyl group, methacrylic group or phenylamino group are preferable. More preferred are silane compounds containing a phenyl group or a methacrylic group. In this case, the in-liquid dispersibility of the silica particles in the silica particle dispersion of the present invention is improved, and the viscosity thereof and the peel strength of the molded product formed therefrom are particularly easily maintained in balance.
  • the silane compound is preferably contained in the silica particle dispersion in an amount of 0.1 to 5% by mass.
  • the content of the silane compound is 0.1% by mass or more, when the silica particle dispersion is included in the resin composition, the compatibility between the hollow silica particles and the resin is increased, and the peel strength of the resin composition is increased. If the amount is 5% by mass or less, it can be suppressed from remaining in the composition and the influence on the physical properties of the resin composition can be reduced.
  • the content of the silane compound in the silica particle dispersion is more preferably 0.2% by mass or more, further preferably 0.3% by mass or more, particularly preferably 0.5% by mass or more, and 4% by mass. It is more preferably at most 3% by mass, even more preferably at most 2% by mass.
  • the silica particle dispersion of the present invention preferably further contains an organic thixotropic agent.
  • the organic thixotropic agent is used to suppress agglomeration and precipitation of hollow silica particles in a silica particle dispersion and a resin composition or slurry containing the silica particle dispersion, and to prevent flux from wetting the cured product of the resin composition or slurry. Added to improve sex.
  • organic thixotropic agents include fatty acid amides (amide wax type) synthesized from vegetable oil fatty acids and amines; surfactant types such as fatty acid esters, polyethers, sulfated oils, and higher alcohol sulfates; polycarbonate. Acid esters; polycarboxylic acid amides; urea-modified compounds are included, but hydrogenated castor oil-based ones called castor oil waxes, and oxidized polyethylene-based waxes that are made by oxidizing polyethylene and introducing polar groups. Not included.
  • One type of organic thixotropic agent may be used alone, or two or more types may be used in combination.
  • Organic thixotropic agents are commercially available, such as BYK®-R606, BYK®-405, BYK®-R605, BYK®-R607, BYK® )-410, BYK (registered trademark) -411, BYK (registered trademark) -415, BYK (registered trademark) -430, BYK (registered trademark) -431, BYK (registered trademark) -7410ET, BYK (registered trademark) - 7411ES (manufactured by BIC Chemie Japan), Talen 1450, Talen 2000, Talen 2200A, Talen 7200-20, Talen 8200-20, Talen 8300-20, Talen 8700-20, Talen BA-600, Flownon SH-290, Examples include Fluonon SH-295S, Fluonon SH-350, Fluonon HR-2, and Fluonon HR-4AF (manufactured by Kyoeisha Kagaku Co., Ltd.).
  • the organic thixotropic agent is preferably contained in the silica particle dispersion in a range of 0.01 to 5% by mass.
  • the content of the organic thixotropic agent is 0.01% by mass or more, the aggregation of hollow silica particles in the dispersion is suppressed, and when the silica particle dispersion is stored, the aggregation of hollow silica particles is suppressed, and the resin When included in a composition, it is possible to suppress accumulation of resin between hollow silica particles. This increases the peel strength of the resin composition.
  • the content of the organic thixotropic agent is 5% by mass or less, it is possible to suppress the organic thixotropic agent from remaining in the composition, thereby reducing the influence on the physical properties of the resin composition.
  • the content of the organic thixotropic agent in the silica particle dispersion is more preferably 0.015% by mass or more, even more preferably 0.05% by mass or more, and more preferably 3% by mass or less, It is more preferably 2.5% by mass or less, particularly preferably 2% by mass or less.
  • the silica particle dispersion of the present invention may contain other optional components within a range that does not impair the effects of the present invention.
  • optional components include other inorganic fillers such as alumina, hardening compositions, and the like.
  • the silica particle dispersion of the present invention preferably has a viscosity of 20 to 20,000 mPa ⁇ s at 25° C. when the solid content concentration of the hollow silica particles is 50% by volume. If the viscosity at 25°C of a silica particle dispersion with a solid content concentration of hollow silica particles of 50% by volume is 20 mPa ⁇ s or more, sedimentation (floating) separation of silica can be prevented, and if it is 20000 mPa ⁇ s or less, silica dispersion can be prevented. It can be used while maintaining its condition.
  • the viscosity is more preferably 50 mPa ⁇ s or more, even more preferably 75 mPa ⁇ s or more, particularly preferably 100 mPa ⁇ s or more, more preferably 15000 mPa ⁇ s or less, even more preferably 12000 mPa ⁇ s or less. , 10,000 mPa ⁇ s or less is particularly preferable.
  • the silica particle dispersion of the present invention is obtained by dispersing hollow silica particle powder in a solvent.
  • the hollow silica particles may be obtained by manufacturing, or commercially available hollow silica particles may be used. Below, a method for producing hollow silica particles and a method for producing a silica particle dispersion using the same will be explained.
  • This oil-in-water emulsion is an emulsion in which an oil phase is dispersed in water, and when a silica raw material is added to this emulsion, the silica raw material adheres to oil droplets, forming oil core-silica shell particles.
  • the method for producing hollow silica particles involves preparing an oil-in-water emulsion containing an aqueous phase, an oil phase, and a surfactant, allowing this oil-in-water emulsion to stand for 0.5 to 240 hours, and then forming a core in the oil-in-water emulsion.
  • the method includes obtaining a hollow silica precursor in which a shell layer containing silica is formed on the outer periphery of the hollow silica precursor, removing a core from the hollow silica precursor, and heat-treating the hollow silica precursor.
  • a first silica raw material is added to an oil-in-water emulsion to form a first-stage shell, and a second silica raw material is added to the emulsion in which the first-stage shell is formed.
  • a shell layer around the outer periphery of the core will also be simply referred to as an emulsion.
  • a dispersion liquid in which oil core-silica shell particles are dispersed is produced by adding the first silica raw material and before the second silica raw material is added, and an oil core after the second silica raw material is added.
  • a dispersion in which silica shell particles are dispersed is also sometimes referred to as an emulsion.
  • the dispersion in which oil core-silica shell particles are dispersed after the latter second silica raw material is added may be equivalent to the hollow silica precursor dispersion.
  • a first silica raw material is added to an oil-in-water emulsion containing an aqueous phase, an oil phase, and a surfactant to form a first shell.
  • the aqueous phase of the emulsion mainly contains water as a solvent. Additives such as a water-soluble organic liquid and a water-soluble resin may be further added to the aqueous phase.
  • the proportion of water in the aqueous phase is preferably 50 to 100% by mass, more preferably 90 to 100% by mass.
  • the oil phase of the emulsion preferably contains a water-insoluble organic liquid that is incompatible with the water phase components. This organic liquid forms droplets in the emulsion and forms the oil-core portion of the hollow silica precursor.
  • organic liquids examples include n-hexane, isohexane, n-heptane, isoheptane, n-octane, isooctane, n-nonane, isononane, n-pentane, isopentane, n-decane, isodecane, n-dodecane, isododecane, and pentadecane.
  • aliphatic hydrocarbons such as, or paraffinic base oils that are mixtures thereof, alicyclic hydrocarbons such as cyclopentane, cyclohexane, and cyclohexene, or naphthenic base oils that are mixtures thereof, benzene, toluene, and xylene.
  • ethylbenzene propylbenzene, cumene, mesitylene, tetralin, aromatic hydrocarbons such as styrene, ethers such as propyl ether, isopropyl ether, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, acetic acid Esters such as isobutyl, n-amyl acetate, isoamyl acetate, butyl lactate, methyl propionate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, butyl butyrate, vegetable oils such as palm oil, soybean oil, rapeseed oil, Examples include fluorine-based solvents such as hydrofluorocarbons, perfluorocarbons, and perfluoropolyethers.
  • polyoxyalkylene glycol which becomes a hydrophobic liquid at the shell formation reaction temperature
  • polypropylene glycol molecular weight 1000 or more
  • copolymers examples include copolymers.
  • polyoxypropylene-polyoxyethylene-polyoxypropylene type block copolymers are preferably used. These may be used alone or in combination of two or more as long as they form an oil phase in a single phase.
  • the organic liquid is preferably a hydrocarbon having 8 to 16 carbon atoms, particularly 9 to 12 carbon atoms.
  • the organic liquid is selected by comprehensively considering operability, fire safety, separation between the hollow silica precursor and the organic liquid, the shape characteristics of the hollow silica particles, and the solubility of the organic liquid in water.
  • Ru Hydrocarbons having 8 to 16 carbon atoms may be linear, branched, or cyclic hydrocarbons as long as they have good chemical stability, and hydrocarbons having different numbers of carbon atoms may be used as a mixture. Good too. As the hydrocarbon, saturated hydrocarbons are preferred, and linear saturated hydrocarbons are more preferred.
  • the flash point of the organic liquid is preferably 20°C or higher, more preferably 40°C or higher. When using an organic liquid with a flash point of less than 20° C., the flash point is too low, so measures must be taken for fire prevention and the working environment.
  • Emulsions contain surfactants to increase emulsion stability.
  • the surfactant is preferably water-soluble or water-dispersible, and is preferably used by being added to the aqueous phase.
  • it is a nonionic surfactant.
  • the nonionic surfactant include the following surfactants.
  • Polyoxyethylene-polyoxypropylene copolymer surfactant Polyoxyethylene sorbitan fatty acid ester surfactant: polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate , Polyoxyethylene higher alcohol ether surfactant: polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene octylphenol ether, polyoxyethylene nonylphenol ether, Polyoxyethylene aliphatic ester surfactant: polyoxyethylene glycol monolaurate, polyoxyethylene glycol monostearate, polyoxyethylene glycol monooleate, Glycerin fatty acid ester surfactant: stearic acid monoglyceride, oleic acid monoglyceride.
  • polyoxyethylene sorbitol fatty acid ester surfactants sucrose fatty acid ester surfactants, polyglycerin fatty acid ester surfactants, polyoxyethylene hydrogenated castor oil surfactants, and the like may be used. These may be used alone or in combination of two or more.
  • a polyoxyethylene-polyoxypropylene copolymer is a block copolymer in which a polyoxyethylene block (EO) and a polyoxypropylene block (PO) are combined.
  • the block copolymer include EO-PO-EO block copolymer, EO-PO block copolymer, etc., and EO-PO-EO block copolymer is preferable.
  • the proportion of oxyethylene units in the EO-PO-EO block copolymer is preferably 20% by mass or more, more preferably 30% by mass or more.
  • the weight average molecular weight of the polyoxyethylene-polyoxypropylene copolymer is preferably 3,000 to 27,000, more preferably 6,000 to 19,000.
  • the total amount of polyoxyethylene blocks is preferably 40 to 90% by mass, and the total amount of polyoxypropylene blocks is preferably 10 to 60% by mass with respect to the entire polyoxyethylene-polyoxypropylene copolymer.
  • the amount of surfactant used depends on conditions such as the type of surfactant, HLB (Hydrophile-lipophile balance), which is an index showing the degree of hydrophilicity or hydrophobicity of surfactant, and the particle size of the target silica particles.
  • HLB Hydrophilicity-lipophile balance
  • the content in the aqueous phase is preferably 500 to 20,000 ppm by mass, more preferably 1,000 to 10,000 ppm by mass.
  • the emulsion can be further stabilized.
  • the amount of surfactant remaining in the hollow silica particles can be reduced.
  • the aqueous phase and oil phase may be blended in a mass ratio of 200:1 to 5:1, preferably 100:1 to 9:1.
  • the method for producing an oil-in-water emulsion is not limited to the following. It can be prepared by adjusting the aqueous phase and the oil phase in advance, adding the oil phase to the aqueous phase, and thoroughly mixing or stirring the mixture. Furthermore, methods such as ultrasonic emulsification, stirring emulsification, and high-pressure emulsification that apply physically strong shearing force can be applied. In addition, there are membrane emulsification methods in which a finely divided oil phase is dispersed in an aqueous phase through a membrane with micropores, a phase inversion emulsification method in which a surfactant is dissolved in an oil phase, and then an aqueous phase is added to emulsify it.
  • phase inversion temperature emulsification method which utilizes the fact that the activator changes from water-soluble to oil-soluble at a temperature near the cloud point.
  • phase inversion temperature emulsification method which utilizes the fact that the activator changes from water-soluble to oil-soluble at a temperature near the cloud point.
  • the oil phase is sufficiently dispersed and emulsified in the aqueous phase.
  • the liquid mixture can be emulsified using a high pressure homogenizer, preferably at a pressure of 10 bar or higher, more preferably 20 bar or higher.
  • the step of forming the first shell it is preferable to perform a step of aging the obtained oil-in-water emulsion.
  • a fine emulsion grows preferentially, the primary particle size of the obtained hollow silica becomes uniform, and the distribution of the primary particle size becomes narrow.
  • the aging time is 0.5 to 240 hours.
  • the aging time is preferably 0.5 to 96 hours, most preferably 0.5 to 48 hours.
  • the aging temperature is preferably 5 to 80°C, more preferably 20 to 70°C, and most preferably 20 to 55°C.
  • a first silica raw material is added to the oil-in-water emulsion.
  • the first silica raw material is selected from the group consisting of, for example, an aqueous solution in which water-soluble silica is dissolved, an aqueous dispersion in which solid silica is dispersed, a mixture thereof, and an alkali metal silicate, an activated silicic acid, and a silicon alkoxide. or an aqueous solution or dispersion thereof.
  • alkali metal silicates, activated silicic acids, and silicon alkoxides, or aqueous solutions or aqueous dispersions thereof are preferred because they are easily available.
  • Examples of the solid silica include silica sol obtained by hydrolyzing an organosilicon compound and commercially available silica sol.
  • Examples of the alkali metal of the alkali metal silicate include lithium, sodium, potassium, rubidium, etc. Among them, sodium is preferred because of its ease of availability and economical reasons. That is, as the alkali metal silicate, sodium silicate is preferable.
  • Sodium silicate has a composition represented by Na2O.nSiO2.mH2O .
  • the ratio of sodium to silicic acid is preferably 1.0 to 4.0, more preferably 2.0 to 3.5, in terms of the Na 2 O/SiO 2 molar ratio n.
  • Activated silicic acid is obtained by subjecting an alkali metal silicate to a cation exchange treatment to replace the alkali metal with hydrogen, and an aqueous solution of this activated silicic acid exhibits weak acidity.
  • a hydrogen type cation exchange resin is preferably used.
  • the alkali metal silicate and active silicic acid are preferably dissolved or dispersed in water before being added to the emulsion.
  • the concentration of the alkali metal silicate and activated silicic acid aqueous solution is preferably 3 to 30% by mass, more preferably 5 to 25% by mass in terms of SiO 2 concentration.
  • tetraalkylsilanes such as tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane are preferably used. It is also possible to obtain composite particles by mixing other metal oxides and the like with the silica raw material.
  • Other metal oxides include titanium dioxide, zinc oxide, cerium oxide, copper oxide, iron oxide, tin oxide, and the like.
  • the above-mentioned silica raw materials may be used alone or in a mixture of two or more.
  • an alkali metal silicate aqueous solution particularly a sodium silicate aqueous solution, as the first silica raw material.
  • the addition of the first silica raw material to the oil-in-water emulsion is preferably carried out under acidic conditions.
  • a silica raw material in an acidic environment fine silica particles are generated and a network is created to form the first layer of coating.
  • the reaction temperature is preferably 80°C or lower to maintain stability of the emulsion, more preferably 70°C or lower, even more preferably 60°C or lower, particularly preferably 50°C or lower, and most preferably 40°C or lower.
  • the temperature is preferably 4°C or higher, more preferably 10°C or higher, even more preferably 15°C or higher, and even more preferably 20°C or higher. Particularly preferred, and most preferred is 25°C or higher.
  • the pH of the oil-in-water emulsion is more preferably less than 3, and even more preferably 2.5 or less, from the viewpoint of making the thickness of the film more uniform and making the silica shell layer of the resulting hollow silica more dense. , and more preferably 1 or more.
  • One way to make the pH of the oil-in-water emulsion acidic is to add an acid.
  • the acid include hydrochloric acid, nitric acid, sulfuric acid, acetic acid, perchloric acid, hydrobromic acid, trichloroacetic acid, dichloroacetic acid, methanesulfonic acid, and benzenesulfonic acid.
  • the amount of the first silica raw material added is 1 to 50 parts by mass of SiO 2 in the first silica raw material with respect to 100 parts by mass of the oil phase contained in the emulsion.
  • the content is preferably 3 to 30 parts by mass, and more preferably 3 to 30 parts by mass.
  • the pH of the emulsion in an acidic state for 1 minute or more, more preferably 5 minutes or more, and still more preferably 10 minutes or more. preferable.
  • the pH of the emulsion to which the first silica raw material is added is maintained at 3 or more and 7 or less (weakly acidic to neutral). This allows the first silica raw material to be immobilized on the surface of the oil droplet.
  • Examples of the base include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkaline earth metal hydroxides such as magnesium hydroxide and calcium hydroxide, ammonia, and amines.
  • alkali metal hydroxides such as sodium hydroxide and potassium hydroxide
  • alkaline earth metal hydroxides such as magnesium hydroxide and calcium hydroxide
  • ammonia and amines.
  • a method of exchanging anions such as halogen ions with hydroxide ions by anion exchange treatment may be used.
  • the base When adding the base, it is preferable to gradually add the base while stirring the emulsion to which the first silica raw material has been added to gradually increase the pH of the emulsion. If stirring is weak or a large amount of base is added at once, the pH of the emulsion may become uneven and the thickness of the first layer may become uneven.
  • This holding time may be 10 minutes or more, preferably 1 hour or more, and may be 4 hours or more.
  • This holding temperature is preferably 100°C or lower in order to maintain the stability of the emulsion, more preferably 95°C or lower, even more preferably 90°C or lower, and particularly preferably 85°C or lower. Further, in order to promote ripening, the holding temperature is preferably 35°C or higher, more preferably 40°C or higher, and particularly preferably 45°C or higher.
  • a second silica raw material is added to the emulsion in the presence of alkali metal ions.
  • the hollow silica precursor is an oil core-silica shell particle.
  • the second silica raw material is added to the emulsion under alkaline conditions.
  • the emulsion is made acidic and then the pH is adjusted from 3 to 7 (weakly acidic to neutral). method is used.
  • the first silica layer obtained by this method is porous and has insufficient density, resulting in low strength.
  • the pH of the emulsion when adding the second silica raw material is preferably 8 or higher, more preferably 8.5 or higher, even more preferably 8.7 or higher, in order to suppress the generation of new fine particles. 9 or more is particularly preferred, and 9 or more is most preferred. Furthermore, if the pH is too high, the solubility of silica increases, so it is preferably 13 or less, more preferably 12.5 or less, even more preferably 12 or less, particularly preferably 11.5 or less, and most preferably 11 or less. preferable.
  • One way to make the pH of the oil-in-water emulsion alkaline is to add a base.
  • the same compounds as those mentioned above are used.
  • the same materials as the above-described first silica raw material may be used alone or in a mixture of two or more.
  • at least one of an aqueous sodium silicate solution and an aqueous activated silicic acid solution is preferably used in the addition of the second silica raw material.
  • a method may be used in which the alkali metal hydroxide is added simultaneously with the second silica raw material.
  • a method may be adopted in which sodium silicate is used as the alkali metal silicate in the second silica raw material.
  • the pH of the emulsion is made alkaline while adding the second silica raw material to add sodium silicate, which is an alkaline component, to the slightly acidic emulsion whose pH is set to 5 or higher after the addition of the first silica raw material. Can be retained. Also, alkali metal ions become present in the emulsion.
  • an acid may be added to adjust the pH.
  • the acid used here may be the same as when adding the first silica raw material.
  • the second silica raw material is added in the presence of alkali metal ions.
  • This alkali metal ion may be derived from the first silica raw material, the second silica raw material, or a base added for pH adjustment, and can also be blended by adding additives to the emulsion.
  • an alkali metal silicate is used as at least one of the first silica raw material and the second silica raw material.
  • alkali metal halides, sulfates, nitrates, fatty acid salts, etc. are used as additives for the emulsion.
  • the second silica raw material may be added, for example, by adding one or both of a sodium silicate aqueous solution and an activated silicic acid aqueous solution to the emulsion after addition of the first silica raw material.
  • a sodium silicate aqueous solution and an activated silicic acid aqueous solution may be added all at once, or may be added in order.
  • the addition of the second silica raw material includes a step of adding a sodium silicate aqueous solution to promote adhesion of the silica raw material onto the first silica layer while adjusting the pH, and an activated silicate aqueous solution.
  • the step of adding can be repeated once or twice or more.
  • the second silica raw material is preferably added to the heated emulsion in order to promote adhesion of the silica raw material onto the first silica layer.
  • the heating temperature is preferably 30°C or higher, more preferably 35°C or higher, even more preferably 40°C or higher, particularly preferably 45°C or higher, and most preferably 50°C or higher, in order to suppress the generation of new fine particles. Since the solubility of silica increases as the temperature increases, the temperature is preferably 100°C or lower, more preferably 95°C or lower, even more preferably 90°C or lower, particularly preferably 85°C or lower, and most preferably 80°C or lower. When a heated emulsion is used, it is preferable to gradually cool the generated emulsion to room temperature (about 23° C.) after adding the second silica raw material. That is, the heating temperature is preferably in the range of 30 to 100°C.
  • the amount of the second silica raw material added is adjusted such that SiO 2 in the second silica raw material is 20 to 500 parts by mass with respect to 100 parts by mass of the oil phase.
  • the amount is preferably adjusted to 40 to 300 parts by mass.
  • the total amount of the first silica raw material and the second silica raw material added is determined based on the amount of the first silica raw material added to 100 parts by mass of the oil phase.
  • the total amount of SiO 2 in the second silica raw material and SiO 2 in the second silica raw material is preferably adjusted to be 30 to 500 parts by mass, more preferably 50 to 300 parts by mass.
  • the silica shell layer of the present invention is mainly composed of silica, but may contain other metal components such as Ti and Zr as necessary for adjusting the refractive index.
  • the method of incorporating other metal components is not particularly limited, but for example, a method of adding a metal sol solution or a metal salt aqueous solution at the same time in the step of adding the silica raw material can be used.
  • a hollow silica precursor dispersion is obtained as described above.
  • Examples of methods for obtaining a hollow silica precursor from a hollow silica precursor dispersion include a method of filtering the dispersion, a method of heating to remove the aqueous phase, and a method of separating the precursor by sedimentation or centrifugation. be.
  • One example is a method in which the dispersion is filtered using a filter of about 0.1 ⁇ m to 5 ⁇ m, and the filtered hollow silica precursor is dried.
  • the obtained hollow silica precursor may be washed with water, acid, alkali, organic solvent, etc.
  • the oil core is removed from the hollow silica precursor and heat treated.
  • Methods for removing the oil core include, for example, burning a hollow silica precursor to burn and decompose the oil, evaporating the oil by drying, adding appropriate additives to decomposing the oil, using organic solvents, etc.
  • There are several methods of extracting oil Among these, a method of burning and decomposing oil by firing a hollow silica precursor with little oil residue is preferred.
  • a method of firing a hollow silica precursor to remove an oil core and heat-treating the hollow silica precursor will be described as an example.
  • the oil core is removed in the first heat treatment, and the shell layer of the hollow silica particles is densified in the second heat treatment.
  • the temperature is preferably 100°C or higher, more preferably 200°C or higher, and most preferably 300°C or higher. If the first stage heat treatment is performed at too high a temperature, the silica shell will become denser and it will be difficult to remove the organic components inside, so it is preferably carried out at a temperature of less than 700°C, preferably 550°C or less, more preferably 530°C or less, The temperature is more preferably 520°C or lower, particularly preferably 510°C or lower, and most preferably 500°C or lower.
  • the first stage heat treatment may be performed once or multiple times.
  • the first heat treatment time is preferably 30 minutes or more, preferably 1 hour or more, more preferably 2 hours or more, and preferably 48 hours or less, more preferably 24 hours or less, and even more preferably 12 hours or less. That is, the first stage heat treatment time is preferably in the range of 30 minutes to 48 hours.
  • the hollow silica particles are baked to densify the shell.
  • the second heat treatment reduces the number of silanol groups on the particle surface and lowers the dielectric loss tangent.
  • the second stage firing temperature is preferably higher than the first stage heat treatment temperature.
  • the second heat treatment When performing the second heat treatment by a standing method, it is preferably carried out at a temperature of 700°C or higher, more preferably 800°C or higher, even more preferably 900°C or higher, and most preferably 1000°C or higher. Furthermore, if the temperature becomes too high, crystallization of amorphous silica occurs and the dielectric constant increases, so it is preferably carried out at 1200°C or lower, more preferably 1150°C or lower, and most preferably 1100°C or lower. That is, it is preferable to perform the second heat treatment at a temperature in the range of 700 to 1200°C.
  • the second stage heat treatment temperature is preferably 200°C or more higher than the first stage heat treatment temperature, more preferably 200 to 800°C higher, and even more preferably 400 to 700°C higher.
  • the second stage heat treatment may be performed once or multiple times.
  • the heat treatment time is preferably 10 minutes or more, more preferably 30 minutes or more, preferably 24 hours or less, more preferably 12 hours or less, and most preferably 6 hours or less. That is, the second heat treatment time is preferably in the range of 10 minutes to 24 hours.
  • a spray combustion method may be used for the second stage heat treatment.
  • the flame temperature at that time is preferably 1000°C or higher, preferably 1200°C or higher, and most preferably 1400°C or higher. Further, the flame temperature is preferably 2000°C or less, more preferably 1800°C or less, and most preferably 1600°C or less. That is, when the spray combustion method is used for the second stage heat treatment, the flame temperature is preferably in the range of 1000 to 2000°C.
  • the hollow silica precursor may be returned to room temperature before the second stage heat treatment, or the hollow silica precursor may be raised to the second stage heat treatment temperature from a state where the first stage firing temperature is maintained. You can warm it up.
  • the hollow silica particles obtained in the above process may be aggregated due to the drying or firing process, they may be crushed to make the aggregate diameter easier to handle, but in the present invention, they may be crushed as is by mixing with the solvent.
  • a silica particle dispersion can be obtained. Examples of crushing methods include a mortar, a dry or wet ball mill, a shaking sieve, a pin mill, a cutter mill, a hammer mill, a knife mill, a roller mill, and a jet mill. Examples include a method using a crusher.
  • the obtained hollow silica particles are mixed with a solvent to obtain a silica particle dispersion.
  • a solvent and powder of hollow silica particles having an average particle diameter in the range of 0.2 to 10 ⁇ m are mixed, the mixed liquid is subjected to a dispersion treatment, and classified to form hollow silica particles. including removing aggregates.
  • the type and amount of the solvent used, the physical properties of the hollow silica particles, the amount used, etc. are as described above.
  • the hollow silica particle powder is preferably mixed in the silica particle dispersion at a ratio of 5 to 80% by volume. If the proportion of hollow silica particles is too small, the productivity of the subsequent concentration step will decrease, and if it is too large, the viscosity of the silica particle dispersion may increase too much and the productivity of dispersion treatment may decrease, so it should be 5 to 80% by volume. A range of is preferred.
  • the amount of hollow silica particles used is more preferably 10% by volume or more, even more preferably 20% by volume or more, more preferably 60% by volume or less, even more preferably 50% by volume or less.
  • a dispersion device used for pigment dispersion, etc. can be used for dispersion of a liquid mixture containing a solvent and hollow silica particles.
  • mixers such as dispers, homomixers, and planetary mixers, homogenizers (M Technique's "Clearmix”, PRIMIX's “Filmix”, etc., Silverson's “Abramix”, etc.), paint conditioners ( Red Devil), colloid mills (PUC Colloid Mill, IKA Colloid Mill MK), corn mills (IKA Corn Mill MKO, etc.), ball mills, sand mills (Shinmaru Enterprises) "Dyno Mill” manufactured by Manufacturer Co., Ltd.), attritor, pearl mill ("DCP Mill” manufactured by Eirich Co., Ltd., etc.), media-type dispersion machines such as Koboru Mill, wet jet mill ("Ginas PY” manufactured by Genus Co., Ltd., “Starburst” manufactured by Sugino Machine Co., Ltd.) , "
  • the temperature during the dispersion treatment is preferably 0 to 100°C.
  • the temperature during the dispersion treatment here refers to the temperature range before and after the treatment.
  • the treatment temperature is more preferably 5°C or higher, even more preferably 10°C or higher, more preferably 90°C or lower, and even more preferably 80°C or lower.
  • the time for the dispersion treatment may be set appropriately depending on the dispersion device used so as not to destroy the hollow structure of the hollow silica particles, but it is preferably carried out for 0.5 to 60 minutes, and 0.5 to 10 minutes. More preferably, 0.5 to 5 minutes is even more preferable.
  • aggregates of hollow silica particles that remained after being unable to be dispersed even during the dispersion treatment are wet classified.
  • wet classification include classification using a sieve or centrifugal force.
  • a sieve it is preferable to classify using a sieve with an opening of 100 ⁇ m or less.
  • the sieve it is preferable to use a metal having a dense lattice structure, such as an electroformed sieve.
  • the opening of the sieve is preferably 100 ⁇ m or less, more preferably 75 ⁇ m or less, even more preferably 50 ⁇ m or less, and particularly preferably 35 ⁇ m or less. Further, the lower limit of the opening of the sieve is preferably 0.2 ⁇ m or more, more preferably 0.5 ⁇ m or more, and even more preferably 1 ⁇ m or more. That is, the opening of the sieve is preferably in the range of 0.2 to 100 ⁇ m.
  • concentration method include vaporization concentration, solid-liquid separation, and the like.
  • a silane coupling agent may be added to the mixture of the solvent and hollow silica particles.
  • the silane coupling agent include the aforementioned silane coupling agents.
  • the silica particle dispersion of the present invention can be mixed with a resin and used as a resin composition.
  • the resin composition preferably contains hollow silica particles in an amount of 5 to 70% by mass, more preferably 10 to 50% by mass.
  • resins examples include epoxy resins, silicone resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, fluororesins, polyamides such as polyimide, polyamideimide, and polyetherimide; polyesters such as polybutylene terephthalate and polyethylene terephthalate; polyphenylene sulfide , aromatic polyester, polysulfone, liquid crystal polymer, polyether sulfone, polycarbonate, maleimide modified resin, ABS resin, AAS (acrylonitrile-acrylic rubber-styrene) resin, AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resin, polytetra One of fluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene cop
  • the resin composition may contain any component other than the above resin.
  • optional components include dispersion aids, surfactants, fillers other than silica, and the like.
  • the dielectric constant thereof is preferably 2.0 to 3.5 at a frequency of 10 GHz, and the lower limit is more preferably 2.2 or more. , more preferably 2.3 or more, and the upper limit is more preferably 3.2 or less, even more preferably 3.0 or less.
  • the dielectric constant of the resin film at a frequency of 10 GHz is within the above range, it has excellent electrical properties and can be expected to be used in electronic equipment, communication equipment, etc.
  • the dielectric loss tangent of the resin film is preferably 0.01 or less at a frequency of 10 GHz, more preferably 0.008 or less, and even more preferably 0.0065 or less.
  • the dielectric loss tangent of the resin film at a frequency of 10 GHz is within the above range, it has excellent electrical properties and can be expected to be used in electronic equipment, communication equipment, etc.
  • the dielectric loss tangent can be measured using a split post dielectric resonator (SPDR) (eg, manufactured by Agilent Technologies).
  • SPDR split post dielectric resonator
  • the resin film has an average linear expansion coefficient of 10 to 50 ppm/°C.
  • the average coefficient of linear expansion is more preferably 12 ppm/°C or higher, even more preferably 15 ppm/°C or higher, more preferably 40 ppm/°C or lower, even more preferably 30 ppm/°C or lower.
  • the average coefficient of linear expansion is determined by heating the above resin film at a load of 5N and a temperature increase rate of 2°C/min from 30°C using a thermomechanical analyzer (for example, "TMA-60" manufactured by Shimadzu Corporation). It is determined by measuring the dimensional change of a sample up to 150°C and calculating the average.
  • a thermomechanical analyzer for example, "TMA-60” manufactured by Shimadzu Corporation.
  • the silica particle dispersion of the present invention can be used as a variety of fillers, and is particularly used as a resin for producing electronic substrates used in electronic devices such as personal computers, notebook computers, and digital cameras, and communication devices such as smartphones and game consoles. It can be suitably used as a filler in compositions.
  • the silica particle dispersion of the present invention can be used in resin compositions, prepregs, metal foil-clad laminates, and printed wiring boards in order to reduce dielectric constant, reduce transmission loss, reduce moisture absorption, and improve peel strength. It is also expected to be applied to resin sheets, adhesive layers, adhesive films, solder resists, bump reflow applications, rewiring insulating layers, die bonding materials, encapsulants, underfills, mold underfills, and laminated inductors.
  • Test Example 1 hollow silica particles were prepared and a silica particle dispersion liquid was prepared using the obtained hollow silica particles.
  • Example 1 "Preparation of emulsion" 4 g of EO-PO-EO block copolymer (Pluronic F68 manufactured by ADEKA) was added to 1250 g of pure water and stirred until dissolved. To this aqueous solution was added 42 g of n-decane in which 4 g of sorbitan acid monooleate (Ionet S-80, manufactured by Sanyo Chemical Co., Ltd.) was dissolved, and the mixture was stirred using an IKA homogenizer until the entire liquid became homogeneous to prepare a crude emulsion.
  • sorbitan acid monooleate Ionet S-80, manufactured by Sanyo Chemical Co., Ltd.
  • This rough emulsion was emulsified at a pressure of 50 bar using a high-pressure emulsifier (LAB1000, manufactured by SMT Co., Ltd.) to produce a fine emulsion with an emulsion diameter of 1 ⁇ m.
  • a high-pressure emulsifier (LAB1000, manufactured by SMT Co., Ltd.) to produce a fine emulsion with an emulsion diameter of 1 ⁇ m.
  • Dispersion in solvent 10 g of the obtained fired fired hollow silica particles and 200 ml of methyl ethyl ketone (MEK) were placed in a 250 ml polybottle (7% by volume of fired fired hollow silica particles, 93% by volume of MEK), and stirred at 30 rpm for 2 hours using a mix rotor.
  • the obtained mixed liquid was spouted three times at a pressure of 50 MPa from a ⁇ 0.1 mm nozzle using a wet atomization device (Starburst Mini manufactured by Sugino Machine Co., Ltd., model number: HJP-25001). repeated.
  • the obtained slurry was passed through an electroforming sieve with an opening of 10 ⁇ m to obtain a silica particle dispersion having a solid content of 6.2% by mass.
  • Example 2 Hollow silica particles were prepared by changing the amount of EO-PO-EO block copolymer (“Pluronic F68” manufactured by ADEKA) to 2 g and the amount of sorbitan acid monooleate (Ionet S-80 manufactured by Sanyo Chemical Co., Ltd.) to 2 g. The experiment was carried out under the same conditions as in Example 1 except for the above.
  • EO-PO-EO block copolymer (“Pluronic F68” manufactured by ADEKA)
  • sorbitan acid monooleate Ionet S-80 manufactured by Sanyo Chemical Co., Ltd.
  • Example 3 The amount of EO-PO-EO block copolymer ("Pluronic F68" manufactured by ADEKA Corporation) was changed to 10 g, and emulsification was performed at a pressure of 100 bar without using sorbitan acid monooleate (Ionet S-80 manufactured by Sanyo Chemical Co., Ltd.). The test was carried out under the same conditions as in Example 1, except that hollow silica particles were prepared and the slurry was passed through an electroforming sieve with an opening of 15 ⁇ m.
  • Pluronic F68 manufactured by ADEKA Corporation
  • Example 4 Example except that the obtained hollow silica precursor was baked at 1100°C for 1 hour (heating time 10°C/min) to produce hollow silica particles, and the slurry was passed through an electroforming sieve with an opening of 15 ⁇ m. It was carried out under the same conditions as 1.
  • Example 5 The process was carried out under the same conditions as in Example 1, except that the obtained hollow silica precursor was fired at 800° C. for 1 hour (heating time: 10° C./min) to produce hollow silica particles.
  • Example 6 The process was carried out under the same conditions as in Example 1, except that the obtained hollow silica precursor was fired at 700° C. for 1 hour (heating time: 10° C./min) to produce hollow silica particles.
  • Example 7 Filtration and washing of the hollow silica precursor were carried out under the same conditions as in Example 1, except that 350 ml of tap water was used instead of ion-exchanged water.
  • Example 8 10 g of hollow fired silica particles obtained in the same manner as in Example 1, 200 ml of methyl ethyl ketone (MEK), and 0.10 g of KBM-503 (3-methacryloxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.) were placed in a 250 ml polybottle. The mixture was stirred for 2 hours at 30 rpm using a mix rotor. The resulting mixed solution was heated at 80°C for 1 hour, cooled, and atomized using a wet atomization device (Starburst Mini manufactured by Sugino Machine Co., Ltd., model number: HJP-25001) through a ⁇ 0.1 mm nozzle.
  • MEK methyl ethyl ketone
  • KBM-503 3-methacryloxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.
  • the operation of ejecting at a pressurizing pressure of 50 MPa was repeated three times.
  • the obtained slurry was passed through an electroforming sieve with an opening of 10 ⁇ m to obtain a silica particle dispersion having a solid content of 6.2% by mass.
  • Example 9 10 g of hollow fired silica particles obtained in the same manner as in Example 1, 200 ml of methyl ethyl ketone (MEK), and 0.020 g of BYK (registered trademark)-R606 (polyhydroxycarboxylic acid ester, manufactured by Big Chemie) were placed in a 250 ml polybottle. The mixture was stirred for 2 hours at 30 rpm using a mix rotor. The obtained mixed liquid was spouted at a pressure of 50 MPa from a ⁇ 0.1 mm nozzle using an 8 wet atomization device (Starburst Mini manufactured by Sugino Machine Co., Ltd., model number: HJP-25001) for 3 times. Repeated times. The obtained slurry was passed through an electroforming sieve with an opening of 10 ⁇ m to obtain a silica particle dispersion having a solid content of 6.2% by mass.
  • MEK methyl ethyl ketone
  • BYK registered trademark
  • Example 10 A silica particle dispersion was obtained in the same manner as in Example 8, except that 0.10 g of KBM-103 (trimethoxyphenylsilane, manufactured by Shin-Etsu Chemical Co., Ltd.) was used instead of KBM-503.
  • KBM-103 trimethoxyphenylsilane, manufactured by Shin-Etsu Chemical Co., Ltd.
  • Example 11 In Example 1, SO-C2 (deflagration method silica with a median diameter of 0.5 ⁇ m, solid silica, manufactured by Admatex) was used instead of the hollow fired silica particles, and the slurry was passed through an electroformed sieve with an opening of 30 ⁇ m. Except for this, the experiment was carried out under the same conditions as in Example 1.
  • SO-C2 deflagration method silica with a median diameter of 0.5 ⁇ m, solid silica, manufactured by Admatex
  • Example 12 In Example 1, the procedure was carried out under the same conditions as in Example 1, except that iM16K (glass balloon with a median diameter of 18 ⁇ m, manufactured by 3M Company) was used instead of the hollow fired silica particles, and the slurry was passed through an electroformed sieve with an opening of 30 ⁇ m. .
  • iM16K glass balloon with a median diameter of 18 ⁇ m, manufactured by 3M Company
  • Example 13 10 g of hollow fired silica particles obtained in Example 1 were used as they were.
  • the average particle diameter (D50), Ar density, He density, specific surface area, sphericity, and viscosity of a 50% by volume dispersion were measured as shown in Table 1. Shown below.
  • Average particle diameter (D50) Hollow silica particles (secondary particles) were measured using a diffraction scattering particle size distribution analyzer (MT3300) manufactured by Microtrac Bell Co., Ltd., and the median value (median diameter, D50) of the particle size distribution (diameter) was measured. The measurement was performed twice and the average value was determined.
  • MT3300 diffraction scattering particle size distribution analyzer
  • Sphericity Obtain a scanning electron microscope image (SEM image) of hollow silica particles observed at an accelerating voltage of 5 kV using S4800 manufactured by Hitachi High-Technology, and from the SEM image, determine the circumference of each of the 100 arbitrary particles.
  • the diameter of the circle (DL) and the diameter of the inscribed circle (DS) are measured, and the ratio of the diameter of the inscribed circle (DS) to the diameter of the circumscribed circle (DL) is calculated from the average value.
  • the sphericity was determined.
  • Viscosity of Silica Particle Dispersion The viscosity of a silica particle dispersion in which the solid content concentration of hollow silica particles was 50% by volume was measured as follows. 100 ml of hollow silica particles and 100 ml of methyl ethyl ketone (MEK) were placed in a 250 ml polybottle, and stirred with a mix rotor at 30 rpm for 2 hours. However, 100 ml of hollow silica particles was prepared using a mass of 100 x d (g) determined from the density d (g/cm 3 ) of the hollow fired silica particles.
  • MEK methyl ethyl ketone
  • the obtained mixed liquid was spouted three times at a pressure of 50 MPa from a ⁇ 0.1 mm nozzle using a wet atomization device (Starburst Mini manufactured by Sugino Machine Co., Ltd., model number: HJP-25001). repeated.
  • the resulting slurry was adjusted to 25° C., and its viscosity was measured using a rotary rheometer (for example, Modular Rheometer PhysicaMCR-301 manufactured by Anton Paar) at a shear rate of 1 rpm for 30 seconds. The viscosity at 30 seconds was determined.
  • PET5011 550 manufactured by Lintec Corporation, thickness 50 ⁇ m
  • the resulting varnish was applied to the release-treated surface of this PET film using an applicator so that the thickness after drying would be 40 ⁇ m, dried in a gear oven at 100°C for 10 minutes, and then cut lengthwise.
  • An uncured laminated film including an uncured resin film (B stage film) measuring 200 mm x width 200 mm x thickness 40 ⁇ m was produced. The obtained uncured laminated film was heated in a gear oven set at 190° C. for 90 minutes to harden the uncured resin film, thereby producing a cured film.
  • the lamination conditions were that the pressure was reduced to 13 hPa or less by reducing the pressure for 30 seconds, and then pressing was performed for 30 seconds at 100° C. and a pressure of 0.8 MPa.
  • Film peeling step The PET film of the laminated structure was peeled off.
  • Curing process The laminate was placed in a gear oven with an internal temperature of 180° C. for 30 minutes to cure the B-stage film and form an insulating layer.
  • evaluation sample B a strip-shaped cut with a width of 1 cm was made on the copper foil side.
  • the substrate was set in a 90° peel tester, the cut edge of the copper plating was picked up with a grip, 20 mm of the copper plating was peeled off, and the peel strength (N/cm) was measured.
  • Examples 1 to 10 had higher peel strength and stronger adhesive strength than Examples 11 and 13. Furthermore, in Examples 1 to 10, the graininess of the coating film was good, and all of them were suitable for practical use. On the other hand, in Examples 11 and 13, the peel strength was low and graininess of the coating film was also observed. In Example 12, it was coated and dried. The paint film peeled off when touched, and when observed under a microscope, the particles were broken into fragments. For this reason, further evaluation was not possible.

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Abstract

The present invention provides a silica particle dispersion liquid that suppresses granulation when formed into a film and that can increase detachment strength. The silica particle dispersion liquid according to the present invention contains hollow silica particles and a solvent. The average particle size of the hollow silica particles is in a range of 0.2-10 μm.

Description

シリカ粒子分散液Silica particle dispersion
　本発明は、溶媒にシリカ粒子を分散させたシリカ粒子分散液に関する。 The present invention relates to a silica particle dispersion in which silica particles are dispersed in a solvent.
　シリカ粒子は、従来、プリント配線基板やパッケージ配線基板等の電子材料、レンズや光学フィルム等の光学材料、触媒や触媒担体等の機能材料、塗料や化粧品等の顔料等の様々な用途に利用されている。中でも、中空シリカ粒子は、低屈折率、低誘電率、低密度等の特性を有することから、接着フィルム、プリプレグ等の絶縁樹脂シート、並びにプリント配線板に形成される絶縁層に用いられる樹脂組成物の低比誘電率化、低誘電正接化、低熱膨張化に利用されている。 Silica particles have traditionally been used in a variety of applications, including electronic materials such as printed wiring boards and package wiring boards, optical materials such as lenses and optical films, functional materials such as catalysts and catalyst carriers, and pigments for paints and cosmetics. ing. Among them, hollow silica particles have characteristics such as low refractive index, low dielectric constant, and low density, so they are suitable for resin compositions used in insulating resin sheets such as adhesive films, prepregs, and insulating layers formed on printed wiring boards. It is used to lower the dielectric constant, dielectric loss tangent, and thermal expansion of materials.
　シリカ粒子は、乾粉の状態で使用すると凝集しやすいため、使用目的に応じて水や樹脂等の溶媒に分散した分散液の形態で用いられ、シリカ粒子分散液や該シリカ粒子分散液を含むスラリーが種々提案されている。 Silica particles tend to aggregate when used in the dry powder state, so depending on the purpose of use, they are used in the form of a dispersion in a solvent such as water or resin. Various proposals have been made.
　例えば、特許文献１には、粒径が１００ｎｍ～２０００ｎｍであるか又は比表面積が２ｍ２／ｇ～３５ｍ２／ｇであり、２００℃で加熱したときに生成する水分量が表面積１ｍ２あたり４０ｐｐｍ以下であり、ビニル基、フェニル基、フェニルアミノ基、炭素数４以上のアルキル基、メタクリル基、又はエポキシ基を有するシラン化合物にて表面処理されているシリカ粒子材料である電子材料用フィラーと、水分を実質的に含有しない液体状の分散媒とを有する電子材料用スラリーが提案されている。 For example, Patent Document 1 states that the particle size is 100 nm to 2000 nm or the specific surface area is 2 m 2 /g to 35 m 2 /g, and the amount of water generated when heated at 200°C is 40 ppm per 1 m 2 of surface area. A filler for electronic materials, which is a silica particle material whose surface is treated with a silane compound having a vinyl group, a phenyl group, a phenylamino group, an alkyl group having 4 or more carbon atoms, a methacrylic group, or an epoxy group; A slurry for electronic materials including a liquid dispersion medium that does not substantially contain water has been proposed.
　特許文献２には、平均粒子径（Ｄｐａ）が３０～２００ｎｍの範囲にあるシリカ系中空微粒子（Ａ）と平均粒子径（Ｄｐｂ）が５～８０ｎｍの範囲にあるシリカ中実微粒子（Ｂ）と溶媒からなり、シリカ系中空微粒子（Ａ）の濃度（ＣＡ）が固形分として０．２～８重量％の範囲にあり、シリカ中実微粒子（Ｂ）の濃度（ＣＢ）が固形分として０．２～８重量％の範囲にあり、シリカ系中空微粒子（Ａ）と、シリカ中実微粒子（Ｂ）との重量比（Ｂ／Ａ）が０．２５～４にある反射防止膜形成用塗布液が提案されている。 Patent Document 2 describes silica-based hollow fine particles (A) having an average particle diameter (Dpa) in the range of 30 to 200 nm, and silica solid fine particles (B) having an average particle diameter (Dpb) in the range of 5 to 80 nm. The concentration (CA) of the silica-based hollow particles (A) is in the range of 0.2 to 8% by weight as a solid content, and the concentration (CB) of the silica solid particles (B) is 0.2 to 8% by weight as a solid content. A coating liquid for forming an anti-reflection film having a weight ratio (B/A) of silica-based hollow fine particles (A) to silica solid fine particles (B) of 0.25 to 4, which is in the range of 2 to 8% by weight. is proposed.
　また、特許文献３には、平均粒子径が５～４０ｎｍであり、かつ中空粒子及び中実粒子の合計粒子数に占める中空粒子数の割合（中空率）が７０％以上であるシリカ系粒子を含むシリカ系粒子の分散液が提案されている。 Furthermore, Patent Document 3 describes silica-based particles having an average particle diameter of 5 to 40 nm and a ratio of the number of hollow particles to the total number of hollow particles and solid particles (hollowness ratio) of 70% or more. Dispersions of silica-based particles have been proposed.
日本国特開２０２０－０９７４９８号公報Japanese Patent Application Publication No. 2020-097498 日本国特開２０１５－１０２６６６号公報Japanese Patent Application Publication No. 2015-102666 日本国特開２０１８－１２３０４３号公報Japanese Patent Application Publication No. 2018-123043
　しかしながら、従来のシリカ粒子分散液は樹脂組成物に含有させて製膜したときにシリカ粒子の粒立ちがしやすく、剥離強度が低くなり、シリカ粒子に期待される効果が得られ難いことがあった。 However, when conventional silica particle dispersions are incorporated into a resin composition and formed into a film, the silica particles tend to clump, resulting in low peel strength, and it is sometimes difficult to obtain the expected effects of silica particles. Ta.
　本発明は上記課題に鑑みてなされたものであり、製膜したときの粒立ちを抑制し、剥離強度を高められるシリカ粒子分散液を提供することを課題とする。 The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a silica particle dispersion liquid that can suppress grain formation during film formation and increase peel strength.
　本発明は、下記（１）～（１１）に関するものである。
（１）中空シリカ粒子と溶媒を含み、前記中空シリカ粒子の平均粒子径が０．２～１０μｍの範囲にあるシリカ粒子分散液。
（２）前記中空シリカ粒子は、アルゴンガスを用いた乾式ピクノメーターによる密度測定により求めた粒子の密度が０．３５～２．００ｇ／ｃｍ３である、前記（１）に記載のシリカ粒子分散液。
（３）前記中空シリカ粒子は、ヘリウムガスを用いた乾式ピクノメーターによる密度測定により求めた粒子の密度が２．００～２．３０ｇ／ｃｍ３である、前記（１）又は（２）に記載のシリカ粒子分散液。
（４）前記中空シリカ粒子は、ＢＥＴ比表面積が１～１００ｍ２／ｇである、前記（１）～（３）のいずれか１つに記載のシリカ粒子分散液。
（５）前記中空シリカ粒子は、真球度が０．７５～１．０である、前記（１）～（４）のいずれか１つに記載のシリカ粒子分散液。
（６）さらに、ビニル基、フェニル基、フェニルアミノ基、炭素数４以上のアルキル基、メタクリル基及びエポキシ基からなる群から選択される少なくとも１つの基を有するシラン化合物を含有する、前記（１）～（５）のいずれか１つに記載のシリカ粒子分散液。
（７）さらに、有機揺変剤を含有する、前記（１）～（６）のいずれか１つに記載のシリカ粒子分散液。
（８）前記溶媒は、水、炭化水素類、アルコール類、酢酸エステル類、ケトン類、セロソルブ類、グリコールエーテル類、塩化炭化水素類及び極性溶媒からなる群から選択される少なくとも１種を含む、前記（１）～（７）のいずれか１つに記載のシリカ粒子分散液。
（９）前記中空シリカ粒子の固形分濃度を５０体積％としたときの２５℃における前記シリカ粒子分散液の粘度が２０～２００００ｍＰａ・ｓである、前記（１）～（８）のいずれか１つに記載のシリカ粒子分散液。
（１０）前記（１）～（９）のいずれか１つに記載のシリカ粒子分散液を含む樹脂組成物。
（１１）溶媒と平均粒子径が０．２～１０μｍの範囲の中空シリカ粒子の粉末とを混合し、混合液を分散処理し、分級して中空シリカ粒子の凝集物を除去する、シリカ粒子分散液の製造方法。 The present invention relates to the following (1) to (11).
(1) A silica particle dispersion containing hollow silica particles and a solvent, the hollow silica particles having an average particle diameter in the range of 0.2 to 10 μm.
(2) The silica particle dispersion according to (1) above, wherein the hollow silica particles have a particle density of 0.35 to 2.00 g/cm 3 as determined by density measurement with a dry pycnometer using argon gas. liquid.
(3) The hollow silica particles described in (1) or (2) above have a particle density of 2.00 to 2.30 g/cm 3 as determined by density measurement with a dry pycnometer using helium gas. silica particle dispersion.
(4) The silica particle dispersion according to any one of (1) to (3) above, wherein the hollow silica particles have a BET specific surface area of 1 to 100 m 2 /g.
(5) The silica particle dispersion according to any one of (1) to (4) above, wherein the hollow silica particles have a sphericity of 0.75 to 1.0.
(6) The above (1) further contains a silane compound having at least one group selected from the group consisting of a vinyl group, a phenyl group, a phenylamino group, an alkyl group having 4 or more carbon atoms, a methacrylic group, and an epoxy group. The silica particle dispersion according to any one of ) to (5).
(7) The silica particle dispersion according to any one of (1) to (6) above, further containing an organic thixotropic agent.
(8) The solvent includes at least one selected from the group consisting of water, hydrocarbons, alcohols, acetate esters, ketones, cellosolves, glycol ethers, chlorinated hydrocarbons, and polar solvents. The silica particle dispersion according to any one of (1) to (7) above.
(9) Any one of (1) to (8) above, wherein the viscosity of the silica particle dispersion at 25°C is 20 to 20,000 mPa·s when the solid content concentration of the hollow silica particles is 50% by volume. The silica particle dispersion described in .
(10) A resin composition containing the silica particle dispersion according to any one of (1) to (9) above.
(11) Silica particle dispersion, in which a solvent and powder of hollow silica particles with an average particle diameter in the range of 0.2 to 10 μm are mixed, the mixed liquid is subjected to dispersion treatment, and aggregates of hollow silica particles are removed by classification. Method of manufacturing liquid.
　本発明のシリカ粒子分散液は、液中に中空シリカ粒子が凝集することなく均一に分散しているので、本発明のシリカ粒子分散液を含む樹脂組成物を製膜したときの粒立ちを抑制でき、また剥離強度を高められる。 In the silica particle dispersion of the present invention, hollow silica particles are uniformly dispersed in the liquid without agglomeration, so grain formation is suppressed when a resin composition containing the silica particle dispersion of the present invention is formed into a film. It also increases the peel strength.
　以下、本発明について説明するが、以下の説明における例示によって本発明は限定されない。なお、本明細書において、数値範囲を示す「～」は、その前後に記載された数値を下限値及び上限値として含むことを意味する。
　また、本明細書において、「質量」は「重量」と同義である。 The present invention will be described below, but the present invention is not limited to the examples given below. In addition, in this specification, "~" indicating a numerical range means that the numerical values written before and after it are included as a lower limit value and an upper limit value.
Moreover, in this specification, "mass" is synonymous with "weight."
＜シリカ粒子分散液＞
　本発明のシリカ粒子分散液は、中空シリカ粒子と溶媒を含み、中空シリカ粒子が平均粒子径が０．２～１０μｍの範囲にあるものである。本発明のシリカ粒子分散液は、前記中空シリカ粒子が凝集することなく均一に分散されており、分散液中の中空シリカ粒子の分散安定性が向上し、樹脂組成物に含有させて製膜したときの粒立ちを抑制できるとともに、剥離強度を高められる。 <Silica particle dispersion>
The silica particle dispersion of the present invention contains hollow silica particles and a solvent, and the hollow silica particles have an average particle diameter in the range of 0.2 to 10 μm. In the silica particle dispersion of the present invention, the hollow silica particles are uniformly dispersed without agglomeration, and the dispersion stability of the hollow silica particles in the dispersion is improved. It is possible to suppress grain formation during peeling and increase peel strength.
（溶媒）
　シリカ粒子分散液の分散媒となる溶媒は、使用目的に応じて任意に選択でき、例えば、水、炭化水素類、アルコール類、酢酸エステル類、ケトン類、セロソルブ類、グリコールエーテル類、塩化炭化水素類、極性溶媒が挙げられる。溶媒は、これらからなる群から選択される少なくとも１種を含むのが好ましい。 (solvent)
The solvent used as the dispersion medium for the silica particle dispersion can be arbitrarily selected depending on the purpose of use, and examples include water, hydrocarbons, alcohols, acetate esters, ketones, cellosolves, glycol ethers, and chlorinated hydrocarbons. and polar solvents. Preferably, the solvent contains at least one selected from the group consisting of these.
　炭化水素類としては、例えば、トルエン、メチルシクロヘキサン、ノルマルへプタン、ｍ－キシレン等が挙げられる。アルコール類としては、例えば、エタノール、イソプロピルアルコール、１－プロピルアルコール、イソブチルアルコール、１－ブタノール、２－ブタノール等が挙げられる。酢酸エステル類としては、例えば、酢酸プロピル、酢酸イソブチル、酢酸ブチル等が挙げられる。ケトン類としては、例えば、メチルエチルケトン、メチルイソブチルケトン、シクロヘキサノン等が挙げられる。セロソルブ類としては、例えば、エチレングリコールモノメチルエーテル、エチレングリコールモノエチルエーテル等が挙げられる。グリコールエーテル類としては、例えば、１－メトキシ－２－プロパノール、１－メトキシプロピル－２－アセテート、１－エトキシ－２－プロパノール、３－エトキシプロピオン酸エチル等が挙げられる。塩化炭化水素類としては、例えば、トリクロロエチレン、テトラクロロエチレン等が挙げられる。極性溶媒としては、例えば、Ｎ－メチル－２－ピロリドンが挙げられる。 Examples of hydrocarbons include toluene, methylcyclohexane, normal heptane, m-xylene, and the like. Examples of alcohols include ethanol, isopropyl alcohol, 1-propyl alcohol, isobutyl alcohol, 1-butanol, 2-butanol, and the like. Examples of acetic acid esters include propyl acetate, isobutyl acetate, butyl acetate, and the like. Examples of ketones include methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. Examples of cellosolves include ethylene glycol monomethyl ether and ethylene glycol monoethyl ether. Examples of glycol ethers include 1-methoxy-2-propanol, 1-methoxypropyl-2-acetate, 1-ethoxy-2-propanol, and ethyl 3-ethoxypropionate. Examples of chlorinated hydrocarbons include trichlorethylene and tetrachloroethylene. Examples of the polar solvent include N-methyl-2-pyrrolidone.
　溶媒は、使用目的の分野に応じて適宜選択すればよい。例えば、電子機器の配線基板の絶縁層に用いる場合は、ケトン類、炭化水素類を用いるのが好ましく、具体的にメチルエチルケトン（ＭＥＫ）、トルエン等を用いるのが好ましい。 The solvent may be appropriately selected depending on the intended field of use. For example, when used in an insulating layer of a wiring board of an electronic device, it is preferable to use ketones and hydrocarbons, and specifically, it is preferable to use methyl ethyl ketone (MEK), toluene, etc.
　また、本発明のシリカ粒子分散液を硬化性組成物に用いる場合は、液状の主剤や硬化剤自体を溶媒に用いてもよい。前記主剤としては、例えば、エポキシ樹脂、ポリフェニレンエーテル樹脂、ポリエステル樹脂、ポリイミド樹脂、フェノール樹脂、オルトジビニルベンゼン樹脂等が挙げられ、硬化剤としては、例えば、ポリアミン系硬化剤、酸無水物系硬化剤、フェノール系硬化剤、活性エステル系硬化剤、過酸化物等が挙げられる。 Furthermore, when the silica particle dispersion of the present invention is used in a curable composition, the liquid main ingredient or curing agent itself may be used as a solvent. Examples of the base resin include epoxy resins, polyphenylene ether resins, polyester resins, polyimide resins, phenol resins, ortho-divinylbenzene resins, and examples of the curing agent include polyamine-based curing agents and acid anhydride-based curing agents. , phenolic curing agents, active ester curing agents, peroxides, and the like.
　溶媒は、シリカ粒子分散液中、２０～９０体積％の範囲で含まれるのが好ましい。溶媒の含有量が２０体積％以上であると中空シリカ粒子を均一に分散させることができ、また分散液の粘度が高くなりすぎないので取扱いがしやすい。また、溶媒の含有量が９０体積％以下であると液状のため、分散状態のまま使用できる。シリカ粒子分散液中の溶媒の含有量は、２５体積％以上であるのがより好ましく、３０体積％以上がさらに好ましく、また、８０体積％以下であるのがより好ましく、７０体積％以下がさらに好ましく、６０体積％以下が特に好ましく、５０体積％以下が最も好ましい。 The solvent is preferably contained in the silica particle dispersion in a range of 20 to 90% by volume. When the content of the solvent is 20% by volume or more, the hollow silica particles can be uniformly dispersed, and the viscosity of the dispersion liquid does not become too high, making it easy to handle. In addition, when the content of the solvent is 90% by volume or less, it is liquid and can be used in a dispersed state. The content of the solvent in the silica particle dispersion is more preferably 25% by volume or more, even more preferably 30% by volume or more, more preferably 80% by volume or less, and even more preferably 70% by volume or less. It is preferably at most 60% by volume, particularly preferably at most 50% by volume.
（中空シリカ粒子）
　中空シリカ粒子は、シリカを含むシェル層（固体膜）を備え、シェル層の内部に空間部を有するシリカ粒子である。中空シリカ粒子がシェル層の内部に空間部を持つことは、透過型電子顕微鏡（ＴＥＭ）観察や走査型電子顕微鏡（ＳＥＭ）観察により確認できる。ＳＥＭ観察の場合は、一部が開口した破損粒子を観察することにより、中空であることが確認できる。
　なお、以下の中空シリカ粒子の物性は、シリカ粒子分散液を乾燥し粉末状のシリカ粒子を得たもので確認できる。 (Hollow silica particles)
Hollow silica particles are silica particles that include a shell layer (solid film) containing silica and have a space inside the shell layer. The fact that the hollow silica particles have a space inside the shell layer can be confirmed by transmission electron microscopy (TEM) observation or scanning electron microscopy (SEM) observation. In the case of SEM observation, it can be confirmed that the particle is hollow by observing a partially opened broken particle.
The physical properties of the hollow silica particles described below can be confirmed by drying a silica particle dispersion to obtain powdery silica particles.
　本明細書において、シェル層が「シリカを含む」とは、シリカ（ＳｉＯ２）が５０質量％以上含まれることを意味する。シェル層の組成は、ＩＣＰ発光分析法やフレーム原子吸光法などによって測定できる。シェル層が含むシリカは８０質量％以上が好ましく、９５質量％以上がより好ましい。上限は理論的に１００質量％である。シェル層が含むシリカは１００質量％未満が好ましく、９９．９９質量％以下がより好ましい。残分としてはアルカリ金属酸化物およびケイ酸塩、アルカリ土類金属酸化物およびケイ酸塩、カーボン等が挙げられる。
　また、「シェル層の内側に空間部を有する」とは、１個の一次粒子の断面を観察した際に、１個の空間部の周囲をシェル層が囲んでいる中空状態を意味する。すなわち中空粒子１個は、大きな空間部を１個とそれを取り囲むシェル層とを有する。 In this specification, the shell layer "contains silica" means that it contains 50% by mass or more of silica (SiO 2 ). The composition of the shell layer can be measured by ICP emission spectrometry, flame atomic absorption spectrometry, or the like. The shell layer contains preferably 80% by mass or more of silica, more preferably 95% by mass or more. The upper limit is theoretically 100% by mass. The silica contained in the shell layer is preferably less than 100% by mass, more preferably 99.99% by mass or less. Residues include alkali metal oxides and silicates, alkaline earth metal oxides and silicates, carbon, and the like.
Moreover, "having a space inside the shell layer" means a hollow state in which the shell layer surrounds one space when the cross section of one primary particle is observed. That is, one hollow particle has one large space and a shell layer surrounding it.
　中空シリカ粒子がシェル内に空間部を有する構造であることで、本発明のシリカ粒子分散液を含有する組成物は、組成物中により多くの空間を確保でき、電子機器等の絶縁層に用いたときには、誘電率を下げられる。 Since the hollow silica particles have a structure in which the shell has a space, the composition containing the silica particle dispersion of the present invention can secure more space in the composition, making it suitable for use in insulating layers of electronic devices, etc. When this happens, the dielectric constant can be lowered.
　本発明のシリカ粒子分散液に分散される中空シリカ粒子の平均粒子径（Ｄ５０、メジアン径）は、０．２～１０μｍである。なお、中空シリカ粒子は、製造時の焼成や乾燥の工程によって一次粒子同士が一部結合するため、中空シリカ粒子は一次粒子が凝集した二次粒子の集合体となっていることが多い。ここでいう中空シリカ粒子の平均粒子径とは二次粒子の粒径をいい、一次粒子とはＴＥＭ観察やＳＥＭ観察によって確認できる、内部に空間部を持つ球状の粒子をいう。 The average particle diameter (D50, median diameter) of the hollow silica particles dispersed in the silica particle dispersion of the present invention is 0.2 to 10 μm. Note that in hollow silica particles, primary particles are partially bonded to each other during the firing and drying steps during production, so hollow silica particles are often an aggregate of secondary particles in which primary particles are aggregated. The average particle diameter of hollow silica particles herein refers to the particle diameter of secondary particles, and primary particles refer to spherical particles with internal spaces that can be confirmed by TEM observation or SEM observation.
　シリカ粒子分散液中の中空シリカ粒子の平均粒子径（Ｄ５０）が０．２～１０μｍの範囲であると、シリカ粒子分散液が取扱いやすい粘度となり、また塗工時に粒立ちしにくいので、樹脂組成物として用いたときに樹脂組成物の剥離強度が適正に保たれる。
　平均粒子径（Ｄ５０）は、０．５μｍ以上であるのが好ましく、１μｍ以上がより好ましく、また８μｍ以下であるのが好ましく、６μｍ以下がより好ましく、５μｍ以下がさらに好ましい。 When the average particle diameter (D50) of the hollow silica particles in the silica particle dispersion is in the range of 0.2 to 10 μm, the silica particle dispersion has a viscosity that is easy to handle, and it is difficult to form particles during coating, so the resin composition When used as a product, the peel strength of the resin composition is maintained appropriately.
The average particle diameter (D50) is preferably 0.5 μm or more, more preferably 1 μm or more, and preferably 8 μm or less, more preferably 6 μm or less, and even more preferably 5 μm or less.
　中空シリカ粒子の平均粒子径（二次粒子の粒径）はレーザー散乱によって測定することが好ましい。ＳＥＭによって凝集径を測定することは、粒子間の境目が不明瞭で、ウエットな状態での分散を反映しないためである。また、コールターカウンターによる測定では、中空粒子と中実粒子での電場変化が異なり、中実粒子に対して対応した数値を出すことが困難であるためである。 The average particle diameter (particle diameter of secondary particles) of hollow silica particles is preferably measured by laser scattering. This is because measuring the agglomerate diameter by SEM does not reflect the dispersion in a wet state because the boundaries between particles are unclear. In addition, in measurements using a Coulter counter, the electric field changes differ between hollow particles and solid particles, making it difficult to obtain values corresponding to solid particles.
　中空シリカ粒子の二次粒子の粗大粒径（Ｄ９０）は、１～３０μｍであることが好ましい。生産効率の観点から、粗大粒径は１μｍ以上であることが好ましい。また、粗大粒径が大きすぎると、樹脂組成物を膜に成型した際、粒立ちの原因となるため、３０μｍ以下であることが好ましい。粗大粒径は、下限は３μｍ以上であることがより好ましく、５μｍ以上が最も好ましく、また上限は３０μｍ以下であることが好ましく、２５μｍ以下がより好ましく、２０μｍ以下がさらに好ましく、１５μｍ以下が最も好ましい。 The coarse particle diameter (D90) of the secondary particles of the hollow silica particles is preferably 1 to 30 μm. From the viewpoint of production efficiency, the coarse particle size is preferably 1 μm or more. Further, if the coarse particle size is too large, it will cause graininess when the resin composition is molded into a film, so it is preferably 30 μm or less. The lower limit of the coarse particle size is more preferably 3 μm or more, most preferably 5 μm or more, and the upper limit is preferably 30 μm or less, more preferably 25 μm or less, even more preferably 20 μm or less, and most preferably 15 μm or less. .
　なお、粗大粒径も上記したように、レーザー散乱によって二次粒子の粒径を測定することにより求められる。 Incidentally, as described above, the coarse particle size is also determined by measuring the particle size of secondary particles by laser scattering.
　また、中空シリカ粒子の一次粒子の大きさは、ＳＥＭ観察によりその粒子径（直径）を直接観察することによって求められるが、一次粒子の大きさの平均値（平均一次粒子径）は５０ｎｍ～１０μｍの範囲であることが好ましい。平均一次粒子径が５０ｎｍ以上であると、比表面積、吸油量および細孔容積の上昇が抑えられ、粒子表面のＳｉＯＨ量と吸着水の増加を抑制できるので、誘電正接が上昇し難くなる。また、平均一次粒子径が１０μｍ以下であると、フィラーとしての取り扱いがしやすい。
　平均一次粒子径は、製造再現性の観点から、下限は、７０ｎｍ以上であることがより好ましく、１００ｎｍ以上がさらに好ましく、また上限は、５μｍ以下であることがより好ましく、３μｍ以下が特に好ましい。 In addition, the size of the primary particles of hollow silica particles can be determined by directly observing the particle size (diameter) using SEM observation, and the average value of the size of the primary particles (average primary particle size) is 50 nm to 10 μm. It is preferable that it is in the range of . When the average primary particle diameter is 50 nm or more, increases in specific surface area, oil absorption, and pore volume can be suppressed, and increases in the amount of SiOH and adsorbed water on the particle surface can be suppressed, making it difficult for the dielectric loss tangent to increase. Moreover, when the average primary particle diameter is 10 μm or less, it is easy to handle as a filler.
From the viewpoint of manufacturing reproducibility, the average primary particle diameter has a lower limit of preferably 70 nm or more, even more preferably 100 nm or more, and an upper limit of 5 μm or less, particularly preferably 3 μm or less.
　中空シリカ粒子の平均一次粒子径は、具体的には、ＳＥＭ画像より１００個の粒子の一次粒子の大きさを測定し、それらを集計して得られた一次粒子の大きさの分布を、全体の一次粒子の大きさの分布と推定する。ＳＥＭ観察により、解凝集が難しい粒子の一次粒子径を直接測定できる。 Specifically, the average primary particle diameter of hollow silica particles is determined by measuring the primary particle size of 100 particles from a SEM image, and calculating the distribution of the primary particle size obtained by aggregating them. is estimated to be the size distribution of the primary particles. By SEM observation, the primary particle diameter of particles that are difficult to deagglomerate can be directly measured.
　本発明の中空シリカ粒子は、上記した平均一次粒子径を有し、その一次粒子のうち、粒子全体の４０％以上が平均一次粒子径±４０％以内の粒子径であるのが好ましい。４０％以上の粒子の粒子径が平均一次粒子径±４０％以内であると、中空シリカ粒子の大きさが均一となるので、中空シリカ粒子のシェルの欠点が生成しにくい。粒子全体の５０％以上が平均一次粒子径±４０％以内であるのがより好ましく、粒子全体の６０％以上が平均一次粒子径±４０％以内であるのがさらに好ましく、粒子全体の７０％以上が平均一次粒子径±４０％以内であるのが特に好ましい。 The hollow silica particles of the present invention have the above-described average primary particle diameter, and it is preferable that 40% or more of the entire particles have a particle diameter within ±40% of the average primary particle diameter. When the particle diameter of 40% or more of the particles is within ±40% of the average primary particle diameter, the size of the hollow silica particles becomes uniform, and shell defects of the hollow silica particles are less likely to occur. It is more preferable that 50% or more of the entire particles have an average primary particle diameter within ±40%, even more preferably that 60% or more of the entire particles have an average primary particle diameter within ±40%, and 70% or more of the entire particles is particularly preferably within ±40% of the average primary particle diameter.
　中空シリカ粒子は、アルゴンガスを用いた乾式ピクノメーターによる密度測定により求めた粒子の密度（以下、Ａｒ密度ともいう。）が０．３５～２．００ｇ／ｃｍ３であるのが好ましい。Ａｒ密度が０．３５ｇ／ｃｍ３以上であると、分散液中での粒子の割れを抑制でき、また樹脂との比重差が大きくなり過ぎないので、シリカ粒子分散液を樹脂と混合した際に樹脂組成物中での分散性を向上できる。Ａｒ密度が２．００ｇ／ｃｍ３以下であると、誘電率の低減効果を発揮しやすいので、電子機器の材料として好ましく利用できる。Ａｒ密度は、０．４０ｇ／ｃｍ３以上であるのがより好ましく、また上限は１．５０ｇ／ｃｍ３以下であるのがより好ましく、１．００ｇ／ｃｍ３以下がさらに好ましい。具田的に、Ａｒ密度は、０．３５～１．５０ｇ／ｃｍ３がより好ましく、０．４０～１．００ｇ／ｃｍ３がさらに好ましい。 The hollow silica particles preferably have a particle density (hereinafter also referred to as Ar density) of 0.35 to 2.00 g/cm 3 as determined by density measurement using a dry pycnometer using argon gas. When the Ar density is 0.35 g/ cm3 or more, cracking of particles in the dispersion can be suppressed, and the difference in specific gravity with the resin will not become too large, so when the silica particle dispersion is mixed with the resin, Dispersibility in the resin composition can be improved. When the Ar density is 2.00 g/cm 3 or less, the effect of reducing the dielectric constant is easily exhibited, so that it can be preferably used as a material for electronic devices. The Ar density is more preferably 0.40 g/cm 3 or more, and the upper limit is more preferably 1.50 g/cm 3 or less, even more preferably 1.00 g/cm 3 or less. According to Guda, the Ar density is more preferably 0.35 to 1.50 g/cm 3 , even more preferably 0.40 to 1.00 g/cm 3 .
　また、中空シリカ粒子は、ヘリウムガスを用いた乾式ピクノメーターによる密度測定により求めた粒子の密度（以下、Ｈｅ密度ともいう。）が２．００～２．３０ｇ／ｃｍ３であるのが好ましい。ヘリウムガスは微細な空隙を透過するため、内部に空間を有するシリカ粒子の、シリカ部分の真密度に対応する密度が得られる。Ｈｅ密度が２．００ｇ／ｃｍ３以上であると、緻密なシリカ粒子であるので、シリカ粒子分散液を樹脂と混合して用いた際に樹脂組成物の剥離強度を低下させることがなく、また中空シリカ粒子に含まれるシラノール残存量が少なくなるため、誘電正接を下げやすい。Ｈｅ密度が２．３０ｇ／ｃｍ３を上回るようなシリカ質を得るにはかなり高い温度での焼成が必要であり、また、粒子が破損しやすくなる。Ｈｅ密度が２．３０ｇ／ｃｍ３以下であると、中空シリカ粒子中に含まれる空間を維持でき、またＡｒ密度を悪化させることがない。Ｈｅ密度は、２．０５ｇ／ｃｍ３以上であるのがより好ましく、２．１０ｇ／ｃｍ３以上がさらに好ましく、また、２．２５ｇ／ｃｍ３以下であるのがより好ましく、２．２３ｇ／ｃｍ３以下がさらに好ましい。具体的に、Ｈｅ密度は、２．０５～２．２５ｇ／ｃｍ３がより好ましく、２．１０～２．２３ｇ／ｃｍ３がさらに好ましい。 Further, the hollow silica particles preferably have a particle density (hereinafter also referred to as He density) of 2.00 to 2.30 g/cm 3 as determined by density measurement using a dry pycnometer using helium gas. Since helium gas permeates through minute voids, a density corresponding to the true density of the silica portion of the silica particles having spaces inside can be obtained. When the He density is 2.00 g/cm 3 or more, the silica particles are dense, so when the silica particle dispersion is mixed with a resin and used, the peel strength of the resin composition will not be reduced, and Since the residual amount of silanol contained in the hollow silica particles is reduced, it is easy to lower the dielectric loss tangent. In order to obtain a siliceous material having a He density of more than 2.30 g/cm 3 , firing at a considerably high temperature is required, and the particles are likely to be damaged. When the He density is 2.30 g/cm 3 or less, the space contained in the hollow silica particles can be maintained, and the Ar density will not be deteriorated. The He density is more preferably 2.05 g/cm 3 or more, even more preferably 2.10 g/cm 3 or more, and more preferably 2.25 g/cm 3 or less, 2.23 g/cm 3 or more. More preferably, it is 3 or less. Specifically, the He density is more preferably 2.05 to 2.25 g/cm 3 , even more preferably 2.10 to 2.23 g/cm 3 .
　中空シリカ粒子の見かけ密度は比重瓶を用いて測定することもできる。比重瓶に試料（中空シリカ粒子）と有機溶媒を入れ、２５℃で４８時間静置後測定する。中空シリカ粒子のシェルの緻密度によっては有機溶媒の浸透に時間を要することもあるため、上記の時間静置することが好ましい。この方法で測定した結果は、アルゴンガスを用いた乾式ピクノメーターによる密度測定の結果と対応する。 The apparent density of hollow silica particles can also be measured using a pycnometer. Put a sample (hollow silica particles) and an organic solvent into a pycnometer, and measure after standing at 25°C for 48 hours. Since it may take some time for the organic solvent to permeate depending on the density of the shell of the hollow silica particles, it is preferable to leave it for the above-mentioned period of time. The results measured by this method correspond to the results of density measurements using a dry pycnometer using argon gas.
　中空シリカ粒子は、一次粒子径と殻の厚みを調整することで粒子の見かけ密度を調整でき、粒子の密度を変えることで、溶媒中に沈降するか、分散し続けるか、上に浮くかを調整できる。溶媒中に分散させたい場合は、溶媒の密度と粒子の見かけ密度が近いことが望ましい。例えば、密度が１．０ｇ／ｃｍ３の水に分散させたい場合は、粒子の見かけ密度を０．８ｇ／ｃｍ３以上１．２ｇ／ｃｍ３以下に調整するのが好ましい。 The apparent density of hollow silica particles can be adjusted by adjusting the primary particle diameter and shell thickness, and by changing the density of the particles, it is possible to determine whether they will settle in the solvent, continue to disperse, or float to the top. Can be adjusted. When dispersing particles in a solvent, it is desirable that the density of the solvent and the apparent density of the particles be close to each other. For example, when dispersing particles in water with a density of 1.0 g/cm 3 , it is preferable to adjust the apparent density of the particles to 0.8 g/cm 3 or more and 1.2 g/cm 3 or less.
　また、中空シリカ粒子は、ＢＥＴ比表面積が１～１００ｍ２／ｇであるのが好ましい。ＢＥＴ比表面積を１ｍ２／ｇ未満とすることは実質的に困難である。また、ＢＥＴ比表面積が大きすぎるとシリカ表面により多くの樹脂等が吸着されるが、ＢＥＴ比表面積が１００ｍ２／ｇ以下であると、樹脂等の吸着多寡を抑制し、樹脂組成物としたときの粘度上昇を抑制できる。ＢＥＴ比表面積は、１～１００ｍ２／ｇが好ましく、１～５０ｍ２／ｇがより好ましく、１～２０ｍ２／ｇがさらに好ましく、１～１５ｍ２／ｇが最も好ましい。 Further, the hollow silica particles preferably have a BET specific surface area of 1 to 100 m 2 /g. It is substantially difficult to reduce the BET specific surface area to less than 1 m 2 /g. In addition, if the BET specific surface area is too large, more resin etc. will be adsorbed on the silica surface, but if the BET specific surface area is 100 m 2 /g or less, the amount of adsorption of resin etc. will be suppressed, and when used as a resin composition. viscosity increase can be suppressed. The BET specific surface area is preferably 1 to 100 m 2 /g, more preferably 1 to 50 m 2 /g, even more preferably 1 to 20 m 2 /g, and most preferably 1 to 15 m 2 /g.
　ここで、ＢＥＴ比表面積の測定は、比表面積測定装置（例えば、株式会社島津製作所製「トライスターＩＩ３０２０」）を用い、前処理として中空シリカ粒子を２３０℃で５０ｍＴｏｒｒとなるまで乾燥させた後、窒素ガスを用いた多点法で測定できる。 Here, the BET specific surface area is measured using a specific surface area measuring device (for example, "Tristar II 3020" manufactured by Shimadzu Corporation), after drying the hollow silica particles at 230 ° C. until the pressure becomes 50 mTorr as a pretreatment. Can be measured using a multi-point method using nitrogen gas.
　中空シリカ粒子は、Ａｒ密度をＡ（ｇ／ｃｍ３）、ＢＥＴ比表面積をＢ（ｍ２／ｇ）としたとき、Ａｒ密度とＢＥＴ比表面積との積（Ａ×Ｂ）が１～１２０ｍ２／ｃｍ３であるのが好ましい。Ａ×Ｂにより中空シリカ粒子を溶媒中に分散させたときの体積当たりの比表面積が示され、例えば、樹脂中に添加したときには、樹脂中の所定体積に中空シリカ粒子が占める部分の比表面積を示す。中空シリカ粒子が上記したＡｒ密度とＢＥＴ比表面積との関係を満たすことで、当該中空シリカ粒子を含有した樹脂組成物を絶縁層に用いたときは、絶縁層の誘電率を下げて、誘電損失を低下できるので、高周波回路に十分対応できる基盤を提供できる。樹脂組成物の粘度が上がり過ぎると絶縁層に用いたときの誘電正接が悪化するおそれがあるが、Ａ×Ｂが１２０ｍ２／ｃｍ３以下であると、組成物中でのシリカの比表面積が小さいため、組成物の粘度が上がり過ぎることがなく、誘電正接の悪化を抑制できる。Ａ×Ｂは、８０ｍ２／ｃｍ３以下であるのが好ましく、４０ｍ２／ｃｍ３以下がより好ましく、２０ｍ２／ｃｍ３以下がさらに好ましい。また、Ａ×Ｂが上記より小さいものを作製することは実質困難である。Ａ×Ｂは、２ｍ２／ｃｍ３以上であるのが好ましく、２．５ｍ２／ｃｍ３以上がより好ましく、３ｍ２／ｃｍ３以上がさらに好ましい。 Hollow silica particles have Ar density and BET specific surface area (A x B) of 1 to 120 m 2 when Ar density is A (g/cm 3 ) and BET specific surface area is B (m 2 /g). /cm 3 is preferred. A×B indicates the specific surface area per volume when hollow silica particles are dispersed in a solvent. For example, when added to a resin, the specific surface area of the portion occupied by the hollow silica particles in a given volume of the resin is show. Since the hollow silica particles satisfy the above relationship between Ar density and BET specific surface area, when a resin composition containing the hollow silica particles is used for the insulating layer, the dielectric constant of the insulating layer is lowered and the dielectric loss is reduced. Since it is possible to lower the current level, it is possible to provide a base that can sufficiently support high-frequency circuits. If the viscosity of the resin composition increases too much, there is a risk that the dielectric loss tangent will deteriorate when used in an insulating layer, but if A×B is 120 m 2 /cm 3 or less, the specific surface area of silica in the composition will decrease. Since it is small, the viscosity of the composition does not increase too much, and deterioration of the dielectric loss tangent can be suppressed. A×B is preferably 80 m 2 /cm 3 or less, more preferably 40 m 2 /cm 3 or less, and even more preferably 20 m 2 /cm 3 or less. Further, it is substantially difficult to manufacture a device with A×B smaller than the above value. A×B is preferably 2 m 2 /cm 3 or more, more preferably 2.5 m 2 /cm 3 or more, and even more preferably 3 m 2 /cm 3 or more.
　中空シリカ粒子の真球度は、０．７５～１．０であることが好ましい。真球度が低くなりすぎると、シリカ粒子分散液を含有した樹脂組成物において樹脂層中のシリカ粒子が接する部材との接地面積が減少して剥離強度が低下する場合があるため、真球度は０．７５以上であるのが好ましい。
　真球度は、走査型電子顕微鏡（ＳＥＭ）により写真撮影して得られる写真投影図における任意の１００個の粒子について、それぞれの最大径（ＤＬ）と、これと直交する最小径（ＤＳ）とを測定し、最大径（ＤＬ）に対する最小径（ＤＳ）の比（ＤＳ／ＤＬ）を算出した平均値で表す。
　分散性などの観点から、真球度は、０．８０以上であることがより好ましく、０．８２以上がさらに好ましく、０．８３以上がよりさらに好ましく、０．８５以上が特に好ましく、０．８７以上が殊更に好ましく、０．９０以上が最も好ましい。 The hollow silica particles preferably have a sphericity of 0.75 to 1.0. If the sphericity becomes too low, the contact area of the silica particles in the resin layer with the member in contact with the resin composition containing the silica particle dispersion may decrease, resulting in a decrease in peel strength. is preferably 0.75 or more.
Sphericity is defined as the maximum diameter (DL) of any 100 particles in a photographic projection obtained by photographing with a scanning electron microscope (SEM), and the minimum diameter (DS) orthogonal to this. is measured, and the ratio of the minimum diameter (DS) to the maximum diameter (DL) (DS/DL) is expressed as the calculated average value.
From the viewpoint of dispersibility etc., the sphericity is more preferably 0.80 or more, even more preferably 0.82 or more, even more preferably 0.83 or more, particularly preferably 0.85 or more, and 0.80 or more. A value of 87 or more is particularly preferred, and a value of 0.90 or more is most preferred.
　中空シリカ粒子のシェル厚さは、一次粒子の直径１に対して、０．０１～０．３であることが好ましい。シェル厚さが一次粒子の直径１に対して０．０１以上であると、中空シリカ粒子の強度を保てる。この比が０．３以下であると、内部の空間部が小さくなり過ぎず、中空形状であることによる特性を発揮できる。
　シェル厚さは、一次粒子の直径１に対して、０．０２以上であることがより好ましく、０．０３以上がさらに好ましく、また０．２以下であることがより好ましく、０．１以下がさらに好ましい。 The shell thickness of the hollow silica particles is preferably 0.01 to 0.3 per diameter 1 of the primary particles. When the shell thickness is 0.01 or more per diameter 1 of the primary particles, the strength of the hollow silica particles can be maintained. When this ratio is 0.3 or less, the internal space does not become too small and the characteristics due to the hollow shape can be exhibited.
The shell thickness is more preferably 0.02 or more, even more preferably 0.03 or more, and more preferably 0.2 or less, and 0.1 or less with respect to the diameter 1 of the primary particle. More preferred.
　ここで、シェル厚さは、透過型電子顕微鏡（ＴＥＭ）によって個々の粒子のシェル厚さを測定することによって求められる。 Here, the shell thickness is determined by measuring the shell thickness of each particle using a transmission electron microscope (TEM).
　中空シリカ粒子は内部に空間部を有するため、粒子内部に物質を内包できる。本発明の中空シリカ粒子はシェル層が緻密であるため各種溶媒が浸透し難いものであるが、破損粒子が存在すると、内部に溶媒が浸入する。よって、破損粒子の割合で吸油量が変化する。 Since hollow silica particles have a space inside, they can contain substances inside the particles. Since the hollow silica particles of the present invention have a dense shell layer, it is difficult for various solvents to penetrate into them, but if there are damaged particles, the solvent will penetrate inside. Therefore, the oil absorption amount changes depending on the proportion of damaged particles.
　中空シリカ粒子の吸油量は、１５～１３００ｍＬ／１００ｇであることが好ましい。吸油量が１５ｍＬ／１００ｇ以上であると樹脂組成物に用いた際に樹脂との密着性が確保でき、１３００ｍＬ／１００ｇ以下であると樹脂組成物に用いた際に樹脂の強度が担保でき、組成物の粘度を低下できる。
　吸油量が多いと粘性が高くなることから、中空シリカ粒子の吸油量は、１０００ｍＬ／１００ｇ以下であることがより好ましく、７００ｍＬ／１００ｇ以下がさらに好ましく、５００ｍＬ／１００ｇ以下が特に好ましく、２００ｍＬ／１００ｇ以下が最も好ましい。また、吸油量が低すぎると粉体と樹脂との密着性が悪化する場合があるため、２０ｍＬ／１００ｇ以上であることがより好ましい。 The oil absorption amount of the hollow silica particles is preferably 15 to 1300 mL/100 g. When the oil absorption amount is 15 mL/100 g or more, adhesion with the resin can be ensured when used in a resin composition, and when it is 1300 mL/100 g or less, the strength of the resin can be ensured when used in a resin composition. Can reduce the viscosity of substances.
Since a large amount of oil absorption increases the viscosity, the oil absorption amount of the hollow silica particles is more preferably 1000 mL/100 g or less, even more preferably 700 mL/100 g or less, particularly preferably 500 mL/100 g or less, and 200 mL/100 g. The following are most preferred. Further, if the oil absorption amount is too low, the adhesion between the powder and the resin may deteriorate, so it is more preferably 20 mL/100 g or more.
　なお、上記したような破損粒子の割合と吸油量との関係から、破損粒子の割合を調整することで吸油量を調整できる。さらに、一次粒子間の空間も油を保持できる空間であることから、一次粒子が凝集した二次粒子のメジアン径が大きいと吸油量が多くなり、二次粒子のメジアン径が小さいと吸油量が少なくなることが考えられる。 Note that, from the relationship between the proportion of damaged particles and the oil absorption amount as described above, the oil absorption amount can be adjusted by adjusting the proportion of damaged particles. Furthermore, since the space between primary particles is also a space that can hold oil, the larger the median diameter of the secondary particles that are agglomerated primary particles, the greater the oil absorption, and the smaller the median diameter of the secondary particles, the greater the oil absorption. It is possible that it will decrease.
　中空シリカ粒子は、Ｌｉ、Ｎａ、Ｋ、Ｒｂ、Ｃｓ、Ｍｇ、Ｃａ、Ｓｒ及びＢａからなる群から選択される１種以上の金属Ｍを含有することが好ましい。中空シリカ粒子に金属Ｍが含まれることで、焼成時にフラックスとして働き、比表面積が低下して誘電正接を低くできる。
　金属Ｍは中空シリカ粒子の製造において、反応工程から洗浄工程の間に含有される。例えば、反応工程において、シリカのシェルを形成する際の反応溶液中に前記金属Ｍの金属塩を添加することや、中空シリカ前駆体を焼き締めする前に前記金属Ｍの金属イオンを含む溶液で洗浄することにより、中空シリカ粒子に金属Ｍを含有できる。 The hollow silica particles preferably contain one or more metals M selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, and Ba. The inclusion of metal M in the hollow silica particles acts as a flux during firing, reduces the specific surface area, and lowers the dielectric loss tangent.
Metal M is contained between the reaction step and the washing step in the production of hollow silica particles. For example, in the reaction step, a metal salt of the metal M may be added to the reaction solution when forming a silica shell, or a solution containing metal ions of the metal M may be added before baking the hollow silica precursor. By washing, the metal M can be contained in the hollow silica particles.
　本発明において、中空シリカ粒子に含まれる金属Ｍの濃度は、５０質量ｐｐｍ以上１質量％以下であることが好ましい。金属Ｍの濃度の総和が５０質量ｐｐｍ以上であると焼成時のフラックス効果により結合シラノール基の縮合が促進され、残存するシラノール基を減らせるので、誘電正接を低下できる。金属Ｍの濃度が高すぎると、シリカと反応してケイ酸塩となる成分が多くなり、中空シリカ粒子の吸湿性が悪化する場合があるため、１質量％以下で含有することが好ましい。金属Ｍの濃度は、１００質量ｐｐｍ以上がより好ましく、１５０ｐｐｍ以上がより好ましく、また、１質量％以下が好ましく、５０００質量ｐｐｍ以下が好ましく、１０００質量ｐｐｍ以下が最も好ましい。 In the present invention, the concentration of metal M contained in the hollow silica particles is preferably 50 mass ppm or more and 1 mass % or less. When the total concentration of metal M is 50 mass ppm or more, the flux effect during firing promotes the condensation of bonded silanol groups, and the remaining silanol groups can be reduced, so that the dielectric loss tangent can be lowered. If the concentration of metal M is too high, the amount of components that react with silica to become silicate increases, which may deteriorate the hygroscopicity of hollow silica particles, so it is preferably contained in an amount of 1% by mass or less. The concentration of metal M is more preferably 100 mass ppm or more, more preferably 150 ppm or more, and preferably 1 mass % or less, preferably 5000 mass ppm or less, and most preferably 1000 mass ppm or less.
　金属Ｍの測定方法は、中空シリカ粒子に過塩素酸とフッ酸を加えて強熱し主成分のケイ素を除去したのちにＩＣＰ発光分析で測定できる。
　また、シリカ原料としてアルカリ金属ケイ酸塩を用いる場合は、シリカ原料としてケイ素アルコキシドを用いる場合に比べて、得られる中空シリカ粒子のシェル層に原料由来の炭素（Ｃ）成分は少なくなる。 Metal M can be measured by ICP emission spectrometry after adding perchloric acid and hydrofluoric acid to hollow silica particles and igniting them to remove the main component, silicon.
Furthermore, when an alkali metal silicate is used as the silica raw material, the carbon (C) component derived from the raw material is reduced in the shell layer of the resulting hollow silica particles, compared to when a silicon alkoxide is used as the silica raw material.
　中空シリカ粒子は、該中空シリカ粒子を含む下記の混練物を下記測定方法により測定したときの粘度が２００００ｍＰａ・ｓ以下であるのが好ましい。
（測定方法）
　アルゴンガスを用いた乾式ピクノメーターによる密度測定により求めた粒子の密度をＡ（ｇ／ｃｍ３）として、煮アマニ油６質量部と中空シリカ粒子（６×Ａ／２．２）質量部を混合し、２０００ｒｐｍで３分間混練して得た混練物を、回転式レオメータを用いてせん断速度１ｓ－１で３０秒測定し、３０秒時点での粘度を求める。 The hollow silica particles preferably have a viscosity of 20,000 mPa·s or less when the following kneaded product containing the hollow silica particles is measured by the following measuring method.
(Measuring method)
Mix 6 parts by mass of boiled linseed oil and 6 parts by mass of hollow silica particles (6×A/2.2), assuming the particle density determined by density measurement with a dry pycnometer using argon gas as A (g/cm 3 ). Then, the kneaded product obtained by kneading at 2000 rpm for 3 minutes was measured for 30 seconds at a shear rate of 1 s -1 using a rotary rheometer, and the viscosity at the 30 second time point was determined.
　上記測定方法により求めた混練物のせん断速度１ｓ－１での粘度が２００００ｍＰａ・ｓ以下であると、中空シリカ粒子を含む樹脂組成物の成形・成膜時に添加する溶剤量を減らせ、乾燥速度を早くでき、生産性を向上できる。また、シリカ粉末の粒径に応じた密度と比表面積の積が大きくなると、樹脂組成物に添加した際に粘度が上昇しやすくなるが、中空シリカ粒子は、密度と比表面積の積が小さいので樹脂組成物の粘度上昇を抑制できる。混練物の粘度は、８０００ｍＰａ・ｓ以下であるのがより好ましく、５０００ｍＰａ・ｓ以下がさらに好ましく、４０００ｍＰａ・ｓ以下が最も好ましい。
　前記混練物のせん断速度１ｓ－１での粘度は、低いほど樹脂組成物の塗工性が向上し、生産性が向上するため下限値は特に限定されない。 If the viscosity of the kneaded product at a shear rate of 1 s −1 determined by the above measurement method is 20,000 mPa·s or less, the amount of solvent added during molding and film formation of the resin composition containing hollow silica particles can be reduced, and the drying rate can be increased. It can be done quickly and productivity can be improved. In addition, when the product of density and specific surface area increases depending on the particle size of silica powder, the viscosity tends to increase when added to a resin composition, but hollow silica particles have a small product of density and specific surface area. Increase in viscosity of the resin composition can be suppressed. The viscosity of the kneaded material is more preferably 8000 mPa·s or less, even more preferably 5000 mPa·s or less, and most preferably 4000 mPa·s or less.
The lower limit of the viscosity of the kneaded product at a shear rate of 1 s -1 is not particularly limited because the lower the viscosity, the better the coating properties of the resin composition and the higher the productivity.
　シリカ粒子は、２９Ｓｉ－ＮＭＲによるスペクトルの帰属において、ＳｉＯ４四面体の連結度合いにより、Ｑ１～Ｑ４で表現される４種の基本構造に分類される。Ｑ１～Ｑ４は、それぞれ以下の通りである。
　Ｑ１は、Ｓｉの周りに酸素を介して１つのＳｉを有する構造単位のことで、ＳｉＯ４四面体が他の１つのＳｉＯ４四面体と連結していて、固体２９Ｓｉ－ＤＤ／ＭＡＳ－ＮＭＲスペクトルにおいて－８０ｐｐｍ付近にピークを有する。
　Ｑ２は、Ｓｉの周りに酸素を介して２つのＳｉを有する構造単位のことで、ＳｉＯ４四面体が他の２つのＳｉＯ４四面体と連結していて、固体２９Ｓｉ－ＤＤ／ＭＡＳ－ＮＭＲスペクトルにおいて－９１ｐｐｍ付近にピークを有する。
　Ｑ３は、Ｓｉの周りに酸素を介して３つのＳｉを有する構造単位のことで、ＳｉＯ４四面体が他の３つのＳｉＯ４四面体と連結していて、固体２９Ｓｉ－ＤＤ／ＭＡＳ－ＮＭＲスペクトルにおいて－１０１ｐｐｍ付近にピークを有する。
　Ｑ４は、Ｓｉの周りに酸素を介して４つのＳｉを有する構造単位のことで、ＳｉＯ４四面体が他の４つのＳｉＯ４四面体と連結していて、固体２９Ｓｉ－ＤＤ／ＭＡＳ－ＮＭＲスペクトルにおいて－１１０ｐｐｍ付近にピークを有する。 Silica particles are classified into four basic structures represented by Q1 to Q4 according to the degree of connection of SiO 4 tetrahedra in the spectrum assignment by 29 Si-NMR. Q1 to Q4 are each as follows.
Q1 is a structural unit that has one Si around Si via oxygen, and a SiO 4 tetrahedron is connected to another SiO 4 tetrahedron, resulting in a solid 29 Si-DD/MAS-NMR The spectrum has a peak around -80 ppm.
Q2 is a structural unit that has two Si around Si via oxygen, and a SiO 4 tetrahedron is connected to two other SiO 4 tetrahedra, resulting in a solid 29 Si-DD/MAS-NMR The spectrum has a peak near -91 ppm.
Q3 is a structural unit that has three Si atoms around Si via oxygen, and a SiO 4 tetrahedron is connected to three other SiO 4 tetrahedra, resulting in a solid 29 Si-DD/MAS-NMR The spectrum has a peak around -101 ppm.
Q4 is a structural unit that has four Si atoms around Si through oxygen, and the SiO 4 tetrahedron is connected to other 4 SiO 4 tetrahedra, resulting in solid 29 Si-DD/MAS-NMR. The spectrum has a peak near -110 ppm.
　本発明の中空シリカ粒子は、固体２９Ｓｉ－ＤＤ／ＭＡＳ－ＮＭＲにより測定した、シラノール基由来のＯＨ基を持たないＱ４構造に対するシラノール基由来のＯＨ基を１つ有するＱ３構造のモル比率（Ｑ３／Ｑ４）が、２～４０％であるのが好ましい。Ｑ３／Ｑ４が４０％以下であると、シラノール量を抑制でき、誘電正接が改善する。Ｑ３／Ｑ４が、２％未満のものを得るのは、高温で焼成する必要があり、その際に中空シリカの中空部が収縮してしまうため、得ることが実質的に難しい。また、Ｑ３／Ｑ４は３０％以下であるのがより好ましく、２０％以下がさらに好ましい。 The hollow silica particles of the present invention have a molar ratio (Q3 /Q4) is preferably 2 to 40%. When Q3/Q4 is 40% or less, the amount of silanol can be suppressed and the dielectric loss tangent is improved. It is substantially difficult to obtain a material with Q3/Q4 of less than 2% because it requires firing at a high temperature and the hollow portion of the hollow silica shrinks during this process. Further, Q3/Q4 is more preferably 30% or less, and even more preferably 20% or less.
　中空シリカ粒子のＱ３／Ｑ４は、以下のように測定する。
　中空シリカ粒子粉末を測定サンプルとする。４００ＭＨｚの核磁気共鳴装置を用い、直径７．５ｍｍのＣＰＳＡＳ用プローブを装着し、観測核を２９Ｓｉとし、ＤＤ／ＭＡＳ法で測定する。測定条件は、２９Ｓｉ共鳴周波数を７９．４３ＭＨｚ、２９Ｓｉ９０°パルス幅を５μ秒、１Ｈ共鳴周波数を３９９．８４ＭＨｚ、１Ｈデカップリング周波数を５０ｋＨｚ、ＭＡＳ回転数を４ｋＨｚ、スペクトル幅を３０．４９ｋＨｚ、測定温度を２３℃とする。データ解析は、フーリエ変換後のスペクトルの各ピークについて、ローレンツ波形とガウス波形の混合により作成したピーク形状の中心位置、高さ、半値幅を可変パラメータとして、非線形最小二乗法により最適化計算を行う。Ｑ１、Ｑ２、Ｑ３及びＱ４の４つの構造単位を対象とし、得られたＱ１の含有率、Ｑ２の含有率、Ｑ３の含有率及びＱ４の含有率から、Ｑ３とＱ４のモル比率を算出する。 Q3/Q4 of hollow silica particles is measured as follows.
A hollow silica particle powder is used as a measurement sample. Using a 400 MHz nuclear magnetic resonance apparatus, a CPSAS probe with a diameter of 7.5 mm is attached, the observation nucleus is 29 Si, and measurements are performed using the DD/MAS method. The measurement conditions were: 29 Si resonance frequency of 79.43 MHz, 29 Si 90° pulse width of 5 μs, 1H resonance frequency of 399.84 MHz, 1H decoupling frequency of 50 kHz, MAS rotation speed of 4 kHz, spectral width of 30.49 kHz, The measurement temperature is 23°C. For data analysis, optimization calculations are performed using the nonlinear least squares method for each peak in the spectrum after Fourier transformation, using the center position, height, and half-width of the peak shape created by mixing the Lorentz waveform and Gaussian waveform as variable parameters. . Targeting the four structural units Q1, Q2, Q3 and Q4, the molar ratio of Q3 and Q4 is calculated from the obtained content of Q1, content of Q2, content of Q3 and content of Q4.
　本実施形態において、シリカ粒子のシラノール基の含有率は、ＣＰＳＡＳ法（Cross Polarization / Magic Angle Spinning）でなく、ＤＤ／ＭＡＳ法（Dipolar Decoupling / Magic Angle Spinning）により測定されたものである。
　ＣＰＳＡＳ法であると、１Ｈが近傍に存在するＳｉを増感して検出するため、得られるピークがＱ１の含有率、Ｑ２の含有率、Ｑ３の含有率及びＱ４の含有率を正確に反映しない。
　一方、ＤＤ／ＭＡＳ法は、ＣＰＳＡＳ法のような増感効果がないため、得られるピークがＱ１の含有率、Ｑ２の含有率、Ｑ３の含有率及びＱ４の含有率を正確に反映し、定量的な解析に適する。 In this embodiment, the content of silanol groups in the silica particles is measured not by the CPSAS method (Cross Polarization/Magic Angle Spinning) but by the DD/MAS method (Dipolar Decoupling/Magic Angle Spinning).
In the CPSAS method, 1 H sensitizes and detects Si present in the vicinity, so the obtained peaks accurately reflect the content of Q1, Q2, Q3, and Q4. do not.
On the other hand, the DD/MAS method does not have a sensitizing effect like the CPSAS method, so the obtained peaks accurately reflect the content of Q1, Q2, Q3, and Q4, and can be quantified. Suitable for analytical analysis.
　中空シリカ粒子の細孔容積は、０．２ｃｍ３／ｇ以下であることが好ましい。
　細孔容積が０．２ｃｍ３／ｇ以下であると、水分を吸着し難く、樹脂組成物の誘電損失の悪化を抑制できる。細孔容積は、０．１５ｃｍ３／ｇ以下であることがより好ましく、０．１ｃｍ３／ｇ以下がさらに好ましく、０．０５ｃｍ３／ｇ以下が特に好ましい。 The pore volume of the hollow silica particles is preferably 0.2 cm 3 /g or less.
When the pore volume is 0.2 cm 3 /g or less, it is difficult to adsorb moisture, and deterioration of dielectric loss of the resin composition can be suppressed. The pore volume is more preferably 0.15 cm 3 /g or less, even more preferably 0.1 cm 3 /g or less, and particularly preferably 0.05 cm 3 /g or less.
　中空シリカ粒子は、その表面がシランカップリング剤によって処理されていてもよい。
　中空シリカ粒子の表面がシランカップリング剤によって処理されていることで、表面シラノール基の残存量が少なくなり、表面が疎水化され、水分吸着を抑えて誘電損失を向上できるとともに、樹脂組成物とする際に、樹脂との親和性が向上し、分散性や、樹脂製膜後の強度が向上する。 The surface of the hollow silica particles may be treated with a silane coupling agent.
Since the surface of the hollow silica particles is treated with a silane coupling agent, the amount of remaining surface silanol groups is reduced, the surface is made hydrophobic, and water adsorption can be suppressed and dielectric loss improved, and the resin composition and When doing so, the affinity with the resin is improved, and the dispersibility and strength after resin film formation are improved.
　表面処理の条件には特に制限はなく、一般的な表面処理条件でよく、湿式処理法や乾式処理法が用いられる。均一な処理を行う観点から、湿式処理法が好ましい。 There are no particular restrictions on the surface treatment conditions, and general surface treatment conditions may be used, and wet treatment methods and dry treatment methods may be used. From the viewpoint of uniform treatment, a wet treatment method is preferred.
　シランカップリング剤の種類としては、アミノシラン系カップリング剤、エポキシシラン系カップリング剤、メルカプトシラン系カップリング剤、シラン系カップリング剤、オルガノシラザン化合物等が挙げられる。シランカップリング剤は１種類を単独で用いてもよいし２種類以上を組み合わせて用いてもよい。 Types of silane coupling agents include aminosilane coupling agents, epoxysilane coupling agents, mercaptosilane coupling agents, silane coupling agents, organosilazane compounds, and the like. One type of silane coupling agent may be used alone, or two or more types may be used in combination.
　具体的に、シランカップリング剤としては、アミノプロピルメトキシシラン、アミノプロピルトリエトキシシラン、ウレイドプロピルトリエトキシシラン、Ｎ－フェニルアミノプロピルトリメトキシシラン、Ｎ－２（アミノエチル）アミノプロピルトリメトキシシラン等のアミノシラン系カップリング剤；グリシドキシプロピルトリメトキシシラン、グリシドキシプロピルトリエトキシシラン、グリシドキシプロピルメチルジエトキシシラン、グリシジルブチルトリメトキシシラン、（３，４－エポキシシクロヘキシル）エチルトリメトキシシラン等のエポキシシラン系カップリング剤；メルカプトプロピルトリメトキシシラン、メルカプトプロピルトリエトキシシラン等のメルカプトシラン系カップリング剤；メチルトリメトキシシラン、ビニルトリメトキシシラン、オクタデシルトリメトキシシラン、フェニルトリメトキシシラン、メタクロキシプロピルトリメトキシシラン、イミダゾールシラン、トリアジンシラン等のシラン系カップリング剤；ＣＦ３（ＣＦ２）７ＣＨ２ＣＨ２Ｓｉ（ＯＣＨ３）３、ＣＦ３（ＣＦ２）７ＣＨ２ＣＨ２ＳｉＣｌ３、ＣＦ３（ＣＦ２）７ＣＨ２ＣＨ２Ｓｉ（ＣＨ３）（ＯＣＨ３）２、ＣＦ３（ＣＦ２）７ＣＨ２ＣＨ２Ｓｉ（ＣＨ３）Ｃ１２、ＣＦ３（ＣＦ２）５ＣＨ２ＣＨ２ＳｉＣｌ３、ＣＦ３（ＣＦ２）５ＣＨ２ＣＨ２Ｓｉ（ＯＣＨ３）３、ＣＦ３ＣＨ２ＣＨ２ＳｉＣｌ３、ＣＦ３ＣＨ２ＣＨ２Ｓｉ（ＯＣＨ３）３、Ｃ８Ｆ１７ＳＯ２Ｎ（Ｃ３Ｈ７）ＣＨ２ＣＨ２ＣＨ２Ｓｉ（ＯＣＨ３）３、Ｃ７Ｆ１５ＣＯＮＨＣＨ２ＣＨ２ＣＨ２Ｓｉ（ＯＣＨ３）３、Ｃ８Ｆ１７ＣＯ２ＣＨ２ＣＨ２ＣＨ２Ｓｉ（ＯＣＨ３）３、Ｃ８Ｆ１７－Ｏ－ＣＦ（ＣＦ３）ＣＦ２－Ｏ－Ｃ３Ｈ６ＳｉＣｌ３、Ｃ３Ｆ７－Ｏ－（ＣＦ（ＣＦ３）ＣＦ２－Ｏ）２－ＣＦ（ＣＦ３）ＣＯＮＨ－（ＣＨ２）３Ｓｉ（ＯＣＨ３）３等のフッ素含有シランカップリング剤；ヘキサメチルジシラザン、ヘキサフェニルジシラザン、トリシラザン、シクロトリシラザン、１，１，３，３，５，５－ヘキサメチルシクロトリシラザン等のオルガノシラザン化合物等が挙げられる。 Specifically, examples of the silane coupling agent include aminopropylmethoxysilane, aminopropyltriethoxysilane, ureidopropyltriethoxysilane, N-phenylaminopropyltrimethoxysilane, N-2 (aminoethyl)aminopropyltrimethoxysilane, etc. Aminosilane coupling agent; glycidoxypropyltrimethoxysilane, glycidoxypropyltriethoxysilane, glycidoxypropylmethyldiethoxysilane, glycidylbutyltrimethoxysilane, (3,4-epoxycyclohexyl)ethyltrimethoxysilane Epoxysilane coupling agents such as mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane; methyltrimethoxysilane, vinyltrimethoxysilane, octadecyltrimethoxysilane, phenyltrimethoxysilane, meth Silane coupling agents such as chloropropyltrimethoxysilane, imidazolesilane , triazinesilane ; CF3 ( CF2 ) 7CH2CH2Si ( OCH3 ) 3 , CF3 ( CF2 ) 7CH2CH2SiCl3 , CF3 ( CF2 ) 7CH2CH2Si ( CH3 ) ( OCH3 ) 2 , CF3 ( CF2 ) 7CH2CH2Si ( CH3 )C12, CF3 ( CF2 ) 5CH 2 CH2SiCl3 , CF3 ( CF2 ) 5CH2CH2Si ( OCH3 ) 3 , CF3CH2CH2SiCl3 , CF3CH2CH2Si ( OCH3 ) 3 , C8F17 SO2N ( C3H7 ) CH2CH2CH2Si ( OCH3 ) 3 , C7F15CONHCH2CH2CH2Si ( OCH3 ) 3 , C8F17CO2CH2CH2CH _ _ _ 2 Si( OCH3 ) 3 , C8F17 -O-CF( CF3 )CF2 - O- C3H6SiCl3 , C3F7 - O-( CF ( CF3 )CF2 - O ) 2 -CF(CF 3 )CONH-(CH 2 ) 3 Si(OCH 3 ) 3 and other fluorine-containing silane coupling agents; hexamethyldisilazane, hexaphenyldisilazane, trisilazane, cyclotrisilazane, 1,1,3 , 3,5,5-hexamethylcyclotrisilazane and other organosilazane compounds.
　シランカップリング剤の付着量としては、中空シリカ粒子の粒子１００質量部に対して、１質量部以上であることが好ましく、１．５質量部以上がより好ましく、２質量部以上がさらに好ましく、また１０質量部以下であることが好ましく、８質量部以下がより好ましく、５質量部以下がさらに好ましい。 The amount of the silane coupling agent attached is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, even more preferably 2 parts by mass or more, based on 100 parts by mass of the hollow silica particles. Moreover, it is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less.
　中空シリカ粒子の表面がシランカップリング剤で処理されていることはＩＲによるシランカップリング剤の置換基によるピークの検出により確認できる。また、シランカップリング剤の付着量は、炭素量により測定できる。 It can be confirmed that the surface of the hollow silica particles has been treated with the silane coupling agent by detecting a peak due to the substituent of the silane coupling agent using IR. Further, the amount of attached silane coupling agent can be measured by the amount of carbon.
　中空シリカ粒子は、１ＧＨｚでの比誘電率が１．３～５．０であるのが好ましい。特に粉体の誘電率測定において、１０ＧＨｚ以上ではサンプルスペースが小さくなり測定精度が悪化するので、本発明では１ＧＨｚでの測定値を採用する。１ＧＨｚでの比誘電率が前記範囲であると、電子機器に求められる低比誘電率を達成できる。なお、１ＧＨｚでの比誘電率が１．３未満の中空シリカ粒子を合成することは、実質的に困難である。
　１ＧＨｚでの比誘電率は、下限が１．３以上であることが好ましく、１．４以上がより好ましい。また上限は４．５以下であることがより好ましく、４．０以下がさらに好ましく、３．５以下がよりさらに好ましく、３．０以下が特に好ましく、２．５以下が最も好ましい。 The hollow silica particles preferably have a dielectric constant of 1.3 to 5.0 at 1 GHz. Particularly in the measurement of the dielectric constant of powder, at frequencies above 10 GHz, the sample space becomes small and the measurement accuracy deteriorates, so in the present invention, measured values at 1 GHz are used. When the dielectric constant at 1 GHz is within the above range, a low dielectric constant required for electronic devices can be achieved. Note that it is substantially difficult to synthesize hollow silica particles having a dielectric constant of less than 1.3 at 1 GHz.
The lower limit of the dielectric constant at 1 GHz is preferably 1.3 or more, more preferably 1.4 or more. Further, the upper limit is more preferably 4.5 or less, even more preferably 4.0 or less, even more preferably 3.5 or less, particularly preferably 3.0 or less, and most preferably 2.5 or less.
　また、中空シリカ粒子は、１ＧＨｚでの誘電正接が０．０００１～０．０５であるのが好ましい。１ＧＨｚでの誘電正接が０．０５以下であると、電子機器に求められる低比誘電率を達成できる。また、１ＧＨｚでの誘電正接が０．０００１未満の中空シリカ粒子を合成することは、実質的に困難である。
　１ＧＨｚでの誘電正接は、下限が０．０００２以上であることがより好ましく、０．０００３以上がさらに好ましい。また上限は０．０１以下であることがより好ましく、０．００５以下がさらに好ましく、０．００３以下がよりさらに好ましく、０．００２以下が特に好ましく、０．００１５以下が殊更に好ましく、０．００１０以下が最も好ましい。 Further, the hollow silica particles preferably have a dielectric loss tangent of 0.0001 to 0.05 at 1 GHz. When the dielectric loss tangent at 1 GHz is 0.05 or less, a low dielectric constant required for electronic devices can be achieved. Further, it is substantially difficult to synthesize hollow silica particles having a dielectric loss tangent of less than 0.0001 at 1 GHz.
The lower limit of the dielectric loss tangent at 1 GHz is more preferably 0.0002 or more, and even more preferably 0.0003 or more. Further, the upper limit is more preferably 0.01 or less, further preferably 0.005 or less, even more preferably 0.003 or less, particularly preferably 0.002 or less, particularly preferably 0.0015 or less, and even more preferably 0.0015 or less. 0010 or less is most preferable.
　比誘電率及び誘電正接は、専用の装置（例えば、キーコム株式会社製「ベクトルネットワークアナライザ　Ｅ５０６３Ａ」）を用い、摂動方式共振器法にて測定できる。 The relative permittivity and dielectric loss tangent can be measured using a perturbation resonator method using a dedicated device (for example, "Vector Network Analyzer E5063A" manufactured by Keycom Co., Ltd.).
　中空シリカ粒子は、シリカ粒子分散液中、５～８０体積％の範囲で含まれるのが好ましい。中空シリカ粒子の含有量が５体積％以上であると樹脂組成物に添加するシリカ粒子分散液の量が少ない量で所望の剥離強度を付与でき、８０体積％以下であると分散液の粘度が上がり過ぎず、取り扱いがしやすい。シリカ粒子分散液中の中空シリカ粒子の含有量は、１０体積％以上であるのがより好ましく、２０体積％以上がさらに好ましく、また７０体積％以下であるのがより好ましく、６０体積％以下がさらに好ましく、５０体積％以下が特に好ましい。 The hollow silica particles are preferably contained in the silica particle dispersion in a range of 5 to 80% by volume. When the content of hollow silica particles is 5% by volume or more, the desired peel strength can be imparted with a small amount of silica particle dispersion added to the resin composition, and when the content is 80% by volume or less, the viscosity of the dispersion is low. It does not rise too much and is easy to handle. The content of hollow silica particles in the silica particle dispersion is more preferably 10% by volume or more, even more preferably 20% by volume or more, and more preferably 70% by volume or less, and 60% by volume or less. It is more preferable, and particularly preferably 50% by volume or less.
（シラン化合物）
　本発明のシリカ粒子分散液には、ビニル基、フェニル基、フェニルアミノ基、炭素数４以上のアルキル基、メタクリル基及びエポキシ基からなる群から選択される少なくとも１つの基を有するシラン化合物を含有するのが好ましい。前記シラン化合物を含有することで、シリカ粒子分散液を樹脂組成物に含有させたときに、樹脂に中空シリカ粒子の表面が馴染むので、より樹脂組成物の剥離強度を高められる。なお、中空シリカ粒子がシランカップリング剤で処理されているときはシラン化合物を必ずしも添加する必要はない。 (silane compound)
The silica particle dispersion of the present invention contains a silane compound having at least one group selected from the group consisting of vinyl group, phenyl group, phenylamino group, alkyl group having 4 or more carbon atoms, methacrylic group, and epoxy group. It is preferable to do so. By containing the silane compound, when the silica particle dispersion is included in the resin composition, the surface of the hollow silica particles blends into the resin, so that the peel strength of the resin composition can be further increased. Note that when the hollow silica particles are treated with a silane coupling agent, it is not necessarily necessary to add a silane compound.
　前記シラン化合物としては、例えば、ビニルシラン、フェニルシラン、フェニルアミノシラン、ヘキシルシラン、デシルシラン、３－メタクリロキシプロピルトリメトキシシラン、アミノプロピルシラン等が挙げられる。これらは１種を単独で使用してもよく、２種以上を組み合わせて用いてもよい。中でも、樹脂との相互作用の観点から、ビニル基、フェニル基、メタクリル基、エポキシ基またはフェニルアミノ基を含むシラン化合物が好ましく、ビニル基、フェニル基、メタクリル基またはフェニルアミノ基を含むシラン化合物がより好ましく、フェニル基またはメタクリル基を含むシラン化合物がさらに好ましい。この場合、本発明のシリカ粒子分散液におけるシリカ粒子の液中分散性が向上し、その粘度と、それから形成される成形物の剥離強度とが特にバランスを保ちやすい。 Examples of the silane compound include vinylsilane, phenylsilane, phenylaminosilane, hexylsilane, decylsilane, 3-methacryloxypropyltrimethoxysilane, and aminopropylsilane. These may be used alone or in combination of two or more. Among these, from the viewpoint of interaction with the resin, silane compounds containing a vinyl group, phenyl group, methacrylic group, epoxy group or phenylamino group are preferable, and silane compounds containing a vinyl group, phenyl group, methacrylic group or phenylamino group are preferable. More preferred are silane compounds containing a phenyl group or a methacrylic group. In this case, the in-liquid dispersibility of the silica particles in the silica particle dispersion of the present invention is improved, and the viscosity thereof and the peel strength of the molded product formed therefrom are particularly easily maintained in balance.
　前記シラン化合物は、シリカ粒子分散液中、０．１～５質量％の範囲で含まれるのが好ましい。シラン化合物の含有量が０．１質量％以上であると、シリカ粒子分散液を樹脂組成物に含有させたときに中空シリカ粒子と樹脂との相溶性を高め、樹脂組成物の剥離強度を高めることができ、５質量％以下であると組成物中への残留を抑えて、樹脂組成物物性への影響を低減できる。シリカ粒子分散液中のシラン化合物の含有量は、０．２質量％以上であるのがより好ましく、０．３質量％以上がさらに好ましく、０．５質量％以上が特に好ましく、また４質量％以下であるのがより好ましく、３質量％以下がさらに好ましく、２質量％以下が特に好ましい。 The silane compound is preferably contained in the silica particle dispersion in an amount of 0.1 to 5% by mass. When the content of the silane compound is 0.1% by mass or more, when the silica particle dispersion is included in the resin composition, the compatibility between the hollow silica particles and the resin is increased, and the peel strength of the resin composition is increased. If the amount is 5% by mass or less, it can be suppressed from remaining in the composition and the influence on the physical properties of the resin composition can be reduced. The content of the silane compound in the silica particle dispersion is more preferably 0.2% by mass or more, further preferably 0.3% by mass or more, particularly preferably 0.5% by mass or more, and 4% by mass. It is more preferably at most 3% by mass, even more preferably at most 2% by mass.
（有機揺変剤）
　本発明のシリカ粒子分散液には、さらに有機揺変剤を含有するのが好ましい。
　有機揺変剤は、シリカ粒子分散液及びシリカ粒子分散液を含有する樹脂組成物やスラリー中での中空シリカ粒子の凝集・沈殿抑制のため、及び樹脂組成物やスラリーの硬化物に対するフラックスのぬれ性向上のために添加される。 (Organic thixotropic agent)
The silica particle dispersion of the present invention preferably further contains an organic thixotropic agent.
The organic thixotropic agent is used to suppress agglomeration and precipitation of hollow silica particles in a silica particle dispersion and a resin composition or slurry containing the silica particle dispersion, and to prevent flux from wetting the cured product of the resin composition or slurry. Added to improve sex.
　有機揺変剤としては、例えば、植物油脂肪酸とアミンより合成される脂肪酸アミド類（アマイドワックス系）；脂肪酸エステル類、ポリエーテル類、硫酸化油、高級アルコールサルフェートなどの界面活性剤系；ポリカルボン酸エステル類；ポリカルボン酸アミド類；尿素変性化合物が含まれるが、ひまし油ワックスと呼ばれる水素添加ひまし油系のもの、及びポリエチレンを酸化処理し、極性基を導入したワックスである酸化ポリエチレン系のものは含まれない。有機揺変剤は、１種を単独で使用してもよく、２種以上を組み合わせて用いてもよい。 Examples of organic thixotropic agents include fatty acid amides (amide wax type) synthesized from vegetable oil fatty acids and amines; surfactant types such as fatty acid esters, polyethers, sulfated oils, and higher alcohol sulfates; polycarbonate. Acid esters; polycarboxylic acid amides; urea-modified compounds are included, but hydrogenated castor oil-based ones called castor oil waxes, and oxidized polyethylene-based waxes that are made by oxidizing polyethylene and introducing polar groups. Not included. One type of organic thixotropic agent may be used alone, or two or more types may be used in combination.
　有機揺変剤は市販品として入手ができ、例えば、ＢＹＫ（登録商標）－Ｒ６０６、ＢＹＫ（登録商標）－４０５、ＢＹＫ（登録商標）－Ｒ６０５、ＢＹＫ（登録商標）－Ｒ６０７、ＢＹＫ（登録商標）－４１０、ＢＹＫ（登録商標）－４１１、ＢＹＫ（登録商標）－４１５、ＢＹＫ（登録商標）－４３０、ＢＹＫ（登録商標）－４３１、ＢＹＫ（登録商標）－７４１０ＥＴ、ＢＹＫ（登録商標）－７４１１ＥＳ（以上、ビックケミー・ジャパン社製）、ターレン１４５０、ターレン２０００、ターレン２２００Ａ、ターレン７２００ー２０、ターレン８２００－２０、ターレン８３００－２０、ターレン８７００－２０、ターレンＢＡ－６００、フローノンＳＨ－２９０、フローノンＳＨ－２９５Ｓ、フローノンＳＨ－３５０、フローノンＨＲ－２、フローノンＨＲ－４ＡＦ（以上、共栄社化学社製）が挙げられる。 Organic thixotropic agents are commercially available, such as BYK®-R606, BYK®-405, BYK®-R605, BYK®-R607, BYK® )-410, BYK (registered trademark) -411, BYK (registered trademark) -415, BYK (registered trademark) -430, BYK (registered trademark) -431, BYK (registered trademark) -7410ET, BYK (registered trademark) - 7411ES (manufactured by BIC Chemie Japan), Talen 1450, Talen 2000, Talen 2200A, Talen 7200-20, Talen 8200-20, Talen 8300-20, Talen 8700-20, Talen BA-600, Flownon SH-290, Examples include Fluonon SH-295S, Fluonon SH-350, Fluonon HR-2, and Fluonon HR-4AF (manufactured by Kyoeisha Kagaku Co., Ltd.).
　有機揺変剤は、シリカ粒子分散液中、０．０１～５質量％の範囲で含まれるのが好ましい。有機揺変剤の含有量が０．０１質量％以上であると分散液中で中空シリカ粒子の凝集が抑制され、シリカ粒子分散液を保管した時に、中空シリカ粒子同士の凝集が抑えられ、樹脂組成物に含有させたときに、中空シリカ粒子間に樹脂が溜まるのを抑制できる。これにより樹脂組成物の剥離強度を高められる。また、有機揺変剤の含有量が５質量％以下であると組成物中への残留を抑えて、樹脂組成物物性への影響を低減できる。シリカ粒子分散液中の有機揺変剤の含有量は、０．０１５質量％以上であるのがより好ましく、０．０５質量％以上がさらに好ましく、また３質量％以下であるのがより好ましく、２．５質量％以下がさらに好ましく、２質量％以下が特に好ましい。 The organic thixotropic agent is preferably contained in the silica particle dispersion in a range of 0.01 to 5% by mass. When the content of the organic thixotropic agent is 0.01% by mass or more, the aggregation of hollow silica particles in the dispersion is suppressed, and when the silica particle dispersion is stored, the aggregation of hollow silica particles is suppressed, and the resin When included in a composition, it is possible to suppress accumulation of resin between hollow silica particles. This increases the peel strength of the resin composition. Further, when the content of the organic thixotropic agent is 5% by mass or less, it is possible to suppress the organic thixotropic agent from remaining in the composition, thereby reducing the influence on the physical properties of the resin composition. The content of the organic thixotropic agent in the silica particle dispersion is more preferably 0.015% by mass or more, even more preferably 0.05% by mass or more, and more preferably 3% by mass or less, It is more preferably 2.5% by mass or less, particularly preferably 2% by mass or less.
　本発明のシリカ粒子分散液は、本発明の効果を損なわない範囲において、その他の任意の成分を含んでもよい。任意成分としては、例えば、アルミナなどの他の無機フィラー、硬化組成物等が挙げられる。 The silica particle dispersion of the present invention may contain other optional components within a range that does not impair the effects of the present invention. Examples of optional components include other inorganic fillers such as alumina, hardening compositions, and the like.
（シリカ粒子分散液の物性）
　本発明のシリカ粒子分散液は、中空シリカ粒子の固形分濃度を５０体積％としたときの２５℃におけるシリカ粒子分散液の粘度が２０～２００００ｍＰａ・ｓであるのが好ましい。
　中空シリカ粒子の固形分濃度が５０体積％のシリカ粒子分散液の２５℃における粘度が２０ｍＰａ・ｓ以上であるとシリカの沈降（浮上）分離を防止でき、２００００ｍＰａ・ｓ以下であるとシリカの分散状態を維持したまま使用できる。前記粘度は、５０ｍＰａ・ｓ以上であるのがより好ましく、７５ｍＰａ・ｓ以上がさらに好ましく、１００ｍＰａ・ｓ以上が特に好ましく、また１５０００ｍＰａ・ｓ以下であるのがより好ましく、１２０００ｍＰａ・ｓ以下がさらに好ましく、１００００ｍＰａ・ｓ以下が特に好ましい。 (Physical properties of silica particle dispersion)
The silica particle dispersion of the present invention preferably has a viscosity of 20 to 20,000 mPa·s at 25° C. when the solid content concentration of the hollow silica particles is 50% by volume.
If the viscosity at 25°C of a silica particle dispersion with a solid content concentration of hollow silica particles of 50% by volume is 20 mPa・s or more, sedimentation (floating) separation of silica can be prevented, and if it is 20000 mPa・s or less, silica dispersion can be prevented. It can be used while maintaining its condition. The viscosity is more preferably 50 mPa·s or more, even more preferably 75 mPa·s or more, particularly preferably 100 mPa·s or more, more preferably 15000 mPa·s or less, even more preferably 12000 mPa·s or less. , 10,000 mPa·s or less is particularly preferable.
＜シリカ粒子分散液の製造方法＞
　本発明のシリカ粒子分散液は、溶媒に中空シリカ粒子の粉末を分散させて得られる。中空シリカ粒子は製造により得てもよいし、市販の中空シリカ粒子を用いてもよい。
　以下に、中空シリカ粒子の製造方法とそれを用いたシリカ粒子分散液の製造方法を説明する。 <Method for producing silica particle dispersion>
The silica particle dispersion of the present invention is obtained by dispersing hollow silica particle powder in a solvent. The hollow silica particles may be obtained by manufacturing, or commercially available hollow silica particles may be used.
Below, a method for producing hollow silica particles and a method for producing a silica particle dispersion using the same will be explained.
（中空シリカ粒子の製造方法）
　中空シリカ粒子の製造方法としては、例えば、水相、油相、及び界面活性剤を含む水中油型エマルションを用い、エマルション中で中空シリカ前駆体を得て、この前駆体から中空シリカ粒子を得る方法が挙げられる。この水中油型エマルションは、水中に油相が分散したエマルションであり、このエマルションにシリカ原料が添加されると油滴にシリカ原料が付着し、オイルコア－シリカシェル粒子を形成できる。 (Method for manufacturing hollow silica particles)
As a method for producing hollow silica particles, for example, an oil-in-water emulsion containing an aqueous phase, an oil phase, and a surfactant is used, a hollow silica precursor is obtained in the emulsion, and hollow silica particles are obtained from this precursor. There are several methods. This oil-in-water emulsion is an emulsion in which an oil phase is dispersed in water, and when a silica raw material is added to this emulsion, the silica raw material adheres to oil droplets, forming oil core-silica shell particles.
　中空シリカ粒子の製造方法は、水相、油相及び界面活性剤を含む水中油型エマルションを作製し、この水中油型エマルションを０．５～２４０時間静置し、水中油型エマルション中でコアの外周にシリカを含むシェル層が形成された中空シリカ前駆体を得て、中空シリカ前駆体からコアを除去し、熱処理することを含む。前記中空シリカ前駆体を得る際には、水中油型エマルションに第１のシリカ原料を添加し、１段目シェルを形成し、１段目シェルが形成されたエマルションに第２のシリカ原料を添加し、２段目シェルを形成することによりコアの外周にシェル層を形成するのが好ましい。
　以下、水中油型エマルションを単にエマルションとも記す。また、第１のシリカ原料が添加されて生成しかつ第２のシリカ原料が添加される前のオイルコア－シリカシェル粒子が分散した分散液、及び、第２のシリカ原料が添加された後のオイルコア－シリカシェル粒子が分散した分散液も、エマルションと記すことがある。後者の第２のシリカ原料が添加された後のオイルコア－シリカシェル粒子が分散した分散液は中空シリカ前駆体分散液と同等のものであってもよい。 The method for producing hollow silica particles involves preparing an oil-in-water emulsion containing an aqueous phase, an oil phase, and a surfactant, allowing this oil-in-water emulsion to stand for 0.5 to 240 hours, and then forming a core in the oil-in-water emulsion. The method includes obtaining a hollow silica precursor in which a shell layer containing silica is formed on the outer periphery of the hollow silica precursor, removing a core from the hollow silica precursor, and heat-treating the hollow silica precursor. When obtaining the hollow silica precursor, a first silica raw material is added to an oil-in-water emulsion to form a first-stage shell, and a second silica raw material is added to the emulsion in which the first-stage shell is formed. However, it is preferable to form a shell layer around the outer periphery of the core by forming a second shell.
Hereinafter, the oil-in-water emulsion will also be simply referred to as an emulsion. Further, a dispersion liquid in which oil core-silica shell particles are dispersed is produced by adding the first silica raw material and before the second silica raw material is added, and an oil core after the second silica raw material is added. - A dispersion in which silica shell particles are dispersed is also sometimes referred to as an emulsion. The dispersion in which oil core-silica shell particles are dispersed after the latter second silica raw material is added may be equivalent to the hollow silica precursor dispersion.
〔１段目シェルの形成〕
　まず、水相、油相、及び界面活性剤を含む水中油型エマルションに第１のシリカ原料を添加し、１段目シェルを形成する。 [Formation of first stage shell]
First, a first silica raw material is added to an oil-in-water emulsion containing an aqueous phase, an oil phase, and a surfactant to form a first shell.
　エマルションの水相は、主として水を溶媒として含む。水相には、水溶性の有機液体、水溶性樹脂等の添加剤がさらに添加されてもよい。水相における水の割合は５０～１００質量％が好ましく、９０～１００質量％がより好ましい。 The aqueous phase of the emulsion mainly contains water as a solvent. Additives such as a water-soluble organic liquid and a water-soluble resin may be further added to the aqueous phase. The proportion of water in the aqueous phase is preferably 50 to 100% by mass, more preferably 90 to 100% by mass.
　エマルションの油相は、水相成分と相溶しない非水溶性の有機液体を含むことが好ましい。この有機液体がエマルション中で液滴となり、中空シリカ前駆体のオイル－コア部分を形成する。 The oil phase of the emulsion preferably contains a water-insoluble organic liquid that is incompatible with the water phase components. This organic liquid forms droplets in the emulsion and forms the oil-core portion of the hollow silica precursor.
　有機液体としては、例えば、ｎ－ヘキサン、イソヘキサン、ｎ－ヘプタン、イソヘプタン、ｎ－オクタン、イソオクタン、ｎ－ノナン、イソノナン、ｎ－ペンタン、イソペンタン、ｎ－デカン、イソデカン、ｎ－ドデカン、イソドデカン、ペンタデカン等の脂肪族炭化水素類、もしくはそれらの混合物であるパラフィン系基油、シクロペンタン、シクロヘキサン、シクロヘキセン等の脂環式炭化水素類、もしくはそれらの混合物であるナフテン系基油、ベンゼン、トルエン、キシレン、エチルベンゼン、プロピルベンゼン、クメン、メシチレン、テトラリン、スチレン等の芳香族炭化水素類、プロピルエーテル、イソプロピルエーテル等のエーテル類、酢酸エチル、酢酸－ｎ－プロピル、酢酸イソプロピル、酢酸－ｎ－ブチル、酢酸イソブチル、酢酸－ｎ－アミル、酢酸イソアミル、乳酸ブチル、プロピオン酸メチル、プロピオン酸エチル、プロピオン酸ブチル、酪酸メチル、酪酸エチル、酪酸ブチル等のエステル類、パーム油、大豆油、菜種油等の植物油、ハイドロフルオロカーボン、パーフルオロカーボン、パーフルオロポリエーテル等のフッ素系溶剤等が挙げられる。また、シェル形成反応温度で疎水性液体となるポリオキシアルキレングリコールを用いることもできる。例えば、ポリプロピレングリコール（分子量１０００以上）、オキシエチレン単位の割合が２０質量％未満で、曇点（１質量％水溶液）が４０℃以下、好ましくは、２０℃以下のポリオキシエチレン－ポリオキシプロピレンブロック共重合体などが挙げられる。中でも、ポリオキシプロピレン－ポリオキシエチレン－ポリオキシプロピレン型のブロック共重合体が好ましく用いられる。
　これらは単独で、又は、単一相で油相を形成する範囲で２種以上を組み合わせて用いてもよい。 Examples of organic liquids include n-hexane, isohexane, n-heptane, isoheptane, n-octane, isooctane, n-nonane, isononane, n-pentane, isopentane, n-decane, isodecane, n-dodecane, isododecane, and pentadecane. aliphatic hydrocarbons such as, or paraffinic base oils that are mixtures thereof, alicyclic hydrocarbons such as cyclopentane, cyclohexane, and cyclohexene, or naphthenic base oils that are mixtures thereof, benzene, toluene, and xylene. , ethylbenzene, propylbenzene, cumene, mesitylene, tetralin, aromatic hydrocarbons such as styrene, ethers such as propyl ether, isopropyl ether, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, acetic acid Esters such as isobutyl, n-amyl acetate, isoamyl acetate, butyl lactate, methyl propionate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, butyl butyrate, vegetable oils such as palm oil, soybean oil, rapeseed oil, Examples include fluorine-based solvents such as hydrofluorocarbons, perfluorocarbons, and perfluoropolyethers. Furthermore, polyoxyalkylene glycol which becomes a hydrophobic liquid at the shell formation reaction temperature can also be used. For example, polypropylene glycol (molecular weight 1000 or more), a polyoxyethylene-polyoxypropylene block in which the proportion of oxyethylene units is less than 20% by mass and the cloud point (1% by mass aqueous solution) is 40°C or less, preferably 20°C or less Examples include copolymers. Among these, polyoxypropylene-polyoxyethylene-polyoxypropylene type block copolymers are preferably used.
These may be used alone or in combination of two or more as long as they form an oil phase in a single phase.
　有機液体としては、炭素数８～１６、特に炭素数９～１２の炭化水素が好ましい。有機液体は、操作性、火気への安全性、中空シリカ前駆体と有機液体との分離性、中空シリカ粒子の形状特性、水への有機液体の溶解性などを総合的に考慮して選定される。炭素数が８～１６の炭化水素は、その化学的安定性が良好であれば、直鎖状、分岐状又は環状の炭化水素であってよく、炭素数の異なる炭化水素を混合して用いてもよい。炭化水素としては、飽和炭化水素が好ましく、直鎖状飽和炭化水素がより好ましい。 The organic liquid is preferably a hydrocarbon having 8 to 16 carbon atoms, particularly 9 to 12 carbon atoms. The organic liquid is selected by comprehensively considering operability, fire safety, separation between the hollow silica precursor and the organic liquid, the shape characteristics of the hollow silica particles, and the solubility of the organic liquid in water. Ru. Hydrocarbons having 8 to 16 carbon atoms may be linear, branched, or cyclic hydrocarbons as long as they have good chemical stability, and hydrocarbons having different numbers of carbon atoms may be used as a mixture. Good too. As the hydrocarbon, saturated hydrocarbons are preferred, and linear saturated hydrocarbons are more preferred.
　有機液体の引火点としては、２０℃以上のものが好ましく、４０℃以上のものがより好ましい。引火点が２０℃未満の有機液体を用いる場合、引火点が低すぎるため、防火上、作業環境上の対策が必要である。 The flash point of the organic liquid is preferably 20°C or higher, more preferably 40°C or higher. When using an organic liquid with a flash point of less than 20° C., the flash point is too low, so measures must be taken for fire prevention and the working environment.
　エマルションは、乳化安定性を高めるために、界面活性剤を含む。界面活性剤は、水溶性又は水分散性が好ましく、水相へ添加して用いることが好ましい。好ましくは、非イオン性界面活性剤である。
　非イオン性界面活性剤としては、例えば、下記の界面活性剤が挙げられる。
　ポリオキシエチレン－ポリオキシプロピレン共重合体系界面活性剤、
　ポリオキシエチレンソルビタン脂肪酸エステル系界面活性剤：ポリオキシエチレンソルビタンモノラウレート、ポリオキシエチレンソルビタンモノパルミテート、ポリオキシエチレンソルビタンモノステアレート、ポリオキシエチレンソルビタントリステアレート、ポリオキシエチレンソルビタンモノオレエート、
　ポリオキシエチレン高級アルコールエーテル系界面活性剤：ポリオキシエチレンラウリルエーテル、ポリオキシエチレンセチルエーテル、ポリオキシエチレンステアリルエーテル、ポリオキシエチレンオレイルエーテル、ポリオキシエチレンオクチルフェノールエーテル、ポリオキシエチレンノニルフェノールエーテル、
　ポリオキシエチレン脂肪族エステル系界面活性剤：ポリオキシエチレングリコールモノラウレート、ポリオキシエチレングリコールモノステアレート、ポリオキシエチレングリコールモノオレエート、
　グリセリン脂肪酸エステル系界面活性剤：ステアリン酸モノグリセライド、オレイン酸モノグリセライド。
　さらに、ポリオキシエチレンソルビトール脂肪酸エステル系界面活性剤、ショ糖脂肪酸エステル系界面活性剤、ポリグリセリン脂肪酸エステル系界面活性剤、ポリオキシエチレン硬化ヒマシ油系界面活性剤等を用いてもよい。
　これらは単独で、又は２種以上を組み合わせて用いてもよい。 Emulsions contain surfactants to increase emulsion stability. The surfactant is preferably water-soluble or water-dispersible, and is preferably used by being added to the aqueous phase. Preferably, it is a nonionic surfactant.
Examples of the nonionic surfactant include the following surfactants.
Polyoxyethylene-polyoxypropylene copolymer surfactant,
Polyoxyethylene sorbitan fatty acid ester surfactant: polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate ,
Polyoxyethylene higher alcohol ether surfactant: polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene octylphenol ether, polyoxyethylene nonylphenol ether,
Polyoxyethylene aliphatic ester surfactant: polyoxyethylene glycol monolaurate, polyoxyethylene glycol monostearate, polyoxyethylene glycol monooleate,
Glycerin fatty acid ester surfactant: stearic acid monoglyceride, oleic acid monoglyceride.
Furthermore, polyoxyethylene sorbitol fatty acid ester surfactants, sucrose fatty acid ester surfactants, polyglycerin fatty acid ester surfactants, polyoxyethylene hydrogenated castor oil surfactants, and the like may be used.
These may be used alone or in combination of two or more.
　上記した非イオン性界面活性剤のなかでも、ソルビタン脂肪酸エステルおよびポリオキシエチレン－ポリオキシプロピレン共重合体系界面活性剤が好ましく用いられる。ポリオキシエチレン－ポリオキシプロピレン共重合体は、ポリオキシエチレンブロック（ＥＯ）とポリオキシプロピレンブロック（ＰＯ）とが結合したブロック共重合体である。ブロック共重合体としては、ＥＯ－ＰＯ－ＥＯブロックコポリマー、ＥＯ－ＰＯブロックコポリマー等が挙げられ、好ましくはＥＯ－ＰＯ－ＥＯブロックコポリマーである。ＥＯ－ＰＯ－ＥＯブロックコポリマーのオキシエチレン単位の割合は、２０質量％以上が好ましく、３０質量％以上がより好ましい。
　ポリオキシエチレン－ポリオキシプロピレン共重合体の重量平均分子量は、３，０００～２７，０００が好ましく、６，０００～１９，０００がより好ましい。
　ポリオキシエチレン－ポリオキシプロピレン共重合体全体に対して、ポリオキシエチレンブロックの合計量は４０～９０質量％が好ましく、ポリオキシプロピレンブロックの合計量は１０～６０質量％が好ましい。 Among the above-mentioned nonionic surfactants, sorbitan fatty acid esters and polyoxyethylene-polyoxypropylene copolymer surfactants are preferably used. A polyoxyethylene-polyoxypropylene copolymer is a block copolymer in which a polyoxyethylene block (EO) and a polyoxypropylene block (PO) are combined. Examples of the block copolymer include EO-PO-EO block copolymer, EO-PO block copolymer, etc., and EO-PO-EO block copolymer is preferable. The proportion of oxyethylene units in the EO-PO-EO block copolymer is preferably 20% by mass or more, more preferably 30% by mass or more.
The weight average molecular weight of the polyoxyethylene-polyoxypropylene copolymer is preferably 3,000 to 27,000, more preferably 6,000 to 19,000.
The total amount of polyoxyethylene blocks is preferably 40 to 90% by mass, and the total amount of polyoxypropylene blocks is preferably 10 to 60% by mass with respect to the entire polyoxyethylene-polyoxypropylene copolymer.
　界面活性剤の使用量は、界面活性剤の種類、界面活性剤の親水性あるいは疎水性の程度を表す指標であるＨＬＢ（Ｈｙｄｒｏｐｈｉｌｅ－ｌｉｐｏｐｈｉｌｅ　ｂａｌａｎｃｅ）、目的とするシリカ粒子の粒子径等の条件により異なるが、水相中の含有量が５００～２０，０００質量ｐｐｍが好ましく、１，０００～１０，０００質量ｐｐｍがより好ましい。水相中の含有量が５００質量ｐｐｍ以上で、エマルションをより安定化できる。また、２０，０００質量ｐｐｍ以下で、中空シリカ粒子に残留する界面活性剤の量を少なくできる。 The amount of surfactant used depends on conditions such as the type of surfactant, HLB (Hydrophile-lipophile balance), which is an index showing the degree of hydrophilicity or hydrophobicity of surfactant, and the particle size of the target silica particles. Although different, the content in the aqueous phase is preferably 500 to 20,000 ppm by mass, more preferably 1,000 to 10,000 ppm by mass. When the content in the aqueous phase is 500 mass ppm or more, the emulsion can be further stabilized. Further, at 20,000 mass ppm or less, the amount of surfactant remaining in the hollow silica particles can be reduced.
　水相と油相とは、質量比で、２００：１～５：１で配合してよく、好ましくは１００：１～９：１である。 The aqueous phase and oil phase may be blended in a mass ratio of 200:1 to 5:1, preferably 100:1 to 9:1.
　水中油型エマルションの作製方法は、以下に限定されない。事前に水相及び油相をそれぞれ調整しておき、水相に油相を添加して、十分に混合ないし撹拌させることで作製できる。さらに物理的に強いせん断力を与える超音波乳化、撹拌式乳化、高圧乳化などの方法を適用できる。また、微細孔を持つ膜を通して微細にした油相を水相中に分散させる膜乳化法や、界面活性剤を油相に溶解させた後に水相を加えて乳化を行う転相乳化法、界面活性剤が曇点付近の温度を境に水溶性から油溶性に変化することを利用した転相温度乳化法などの方法がある。これらの乳化方法は、目的とする粒子径、粒度分布等の特定により適宜選択できる。 The method for producing an oil-in-water emulsion is not limited to the following. It can be prepared by adjusting the aqueous phase and the oil phase in advance, adding the oil phase to the aqueous phase, and thoroughly mixing or stirring the mixture. Furthermore, methods such as ultrasonic emulsification, stirring emulsification, and high-pressure emulsification that apply physically strong shearing force can be applied. In addition, there are membrane emulsification methods in which a finely divided oil phase is dispersed in an aqueous phase through a membrane with micropores, a phase inversion emulsification method in which a surfactant is dissolved in an oil phase, and then an aqueous phase is added to emulsify it. There are methods such as the phase inversion temperature emulsification method, which utilizes the fact that the activator changes from water-soluble to oil-soluble at a temperature near the cloud point. These emulsification methods can be appropriately selected depending on the target particle size, particle size distribution, etc.
　得られる中空シリカ粒子を小粒子径化し、粒度分布を狭めるために、水相中に油相が十分に分散し乳化されることが好ましい。例えば、混合液は、好ましくは１０ｂａｒ以上、より好ましくは２０ｂａｒ以上の圧力で高圧ホモジナイザーを用いて乳化できる。 In order to reduce the particle size of the obtained hollow silica particles and narrow the particle size distribution, it is preferable that the oil phase is sufficiently dispersed and emulsified in the aqueous phase. For example, the liquid mixture can be emulsified using a high pressure homogenizer, preferably at a pressure of 10 bar or higher, more preferably 20 bar or higher.
　１段目シェルの形成工程では、得られた水中油型エマルションをエージングする工程を行うのが好ましい。エージングを行うことで、微小なエマルションが優先的に成長し、得られる中空シリカの１次粒径が均一になり、一次粒子径の分布が狭くなる。これにより、Ａｒ密度ＡとＢＥＴ比表面積Ｂとの積（Ａ×Ｂ）を小さくできる。エージングの時間は、０．５～２４０時間である。エージングの時間が０．５時間以上であると、一次粒子の粒径の均一性が高まり、２４０時間以内であると、生産性が良い。エージングの時間は、０．５～９６時間であるのが好ましく、０．５～４８時間が最も好ましい。
　また、エージングの温度は、５～８０℃が好ましく、２０～７０℃がより好ましく、２０～５５℃が最も好ましい。 In the step of forming the first shell, it is preferable to perform a step of aging the obtained oil-in-water emulsion. By performing aging, a fine emulsion grows preferentially, the primary particle size of the obtained hollow silica becomes uniform, and the distribution of the primary particle size becomes narrow. Thereby, the product (A×B) of Ar density A and BET specific surface area B can be made small. The aging time is 0.5 to 240 hours. When the aging time is 0.5 hours or more, the uniformity of the particle size of the primary particles increases, and when the aging time is 240 hours or less, productivity is good. The aging time is preferably 0.5 to 96 hours, most preferably 0.5 to 48 hours.
Furthermore, the aging temperature is preferably 5 to 80°C, more preferably 20 to 70°C, and most preferably 20 to 55°C.
　１段目シェルの形成工程では、水中油型エマルションに、第１のシリカ原料を添加する。
　第１のシリカ原料としては、例えば、水溶性シリカが溶解した水溶液、固体シリカが分散した水性分散液、これらの混合物、ならびに、アルカリ金属ケイ酸塩、活性ケイ酸及びケイ素アルコキシドからなる群から選ばれる１種以上またはそれらの水溶液または水分散液が挙げられる。これらのうちアルカリ金属ケイ酸塩、活性ケイ酸及びケイ素アルコキシドからなる群から選ばれる１種以上またはそれらの水溶液または水分散液が、入手容易性が高い点で好ましい。 In the step of forming the first shell, a first silica raw material is added to the oil-in-water emulsion.
The first silica raw material is selected from the group consisting of, for example, an aqueous solution in which water-soluble silica is dissolved, an aqueous dispersion in which solid silica is dispersed, a mixture thereof, and an alkali metal silicate, an activated silicic acid, and a silicon alkoxide. or an aqueous solution or dispersion thereof. Among these, one or more selected from the group consisting of alkali metal silicates, activated silicic acids, and silicon alkoxides, or aqueous solutions or aqueous dispersions thereof, are preferred because they are easily available.
　固体シリカとしては、例えば、有機ケイ素化合物を加水分解して得られたシリカゾル、市販のシリカゾルが挙げられる。
　アルカリ金属ケイ酸塩のアルカリ金属としては、リチウム、ナトリウム、カリウム、ルビジウム等が挙げられ、中でも入手の容易さ、経済的理由によりナトリウムが好ましい。すなわちアルカリ金属ケイ酸塩としては、ケイ酸ナトリウムが好ましい。ケイ酸ナトリウムは、Ｎａ２Ｏ・ｎＳｉＯ２・ｍＨ２Ｏで表される組成を有する。ナトリウムとケイ酸の割合は、Ｎａ２Ｏ／ＳｉＯ２のモル比ｎで１．０～４．０が好ましく、さらには２．０～３．５が好ましい。 Examples of the solid silica include silica sol obtained by hydrolyzing an organosilicon compound and commercially available silica sol.
Examples of the alkali metal of the alkali metal silicate include lithium, sodium, potassium, rubidium, etc. Among them, sodium is preferred because of its ease of availability and economical reasons. That is, as the alkali metal silicate, sodium silicate is preferable. Sodium silicate has a composition represented by Na2O.nSiO2.mH2O . The ratio of sodium to silicic acid is preferably 1.0 to 4.0, more preferably 2.0 to 3.5, in terms of the Na 2 O/SiO 2 molar ratio n.
　活性ケイ酸はアルカリ金属ケイ酸塩を陽イオン交換処理によりアルカリ金属を水素に置換して得られるものであり、この活性ケイ酸の水溶液は弱酸性を示す。陽イオン交換には、水素型陽イオン交換樹脂が好ましく用いられる。
　アルカリ金属ケイ酸塩及び活性ケイ酸は、水に溶解ないし分散させてから、エマルションに添加することが好ましい。アルカリ金属ケイ酸塩及び活性ケイ酸水溶液の濃度は、ＳｉＯ２濃度として３～３０質量％が好ましく、さらには５～２５質量％が好ましい。 Activated silicic acid is obtained by subjecting an alkali metal silicate to a cation exchange treatment to replace the alkali metal with hydrogen, and an aqueous solution of this activated silicic acid exhibits weak acidity. For cation exchange, a hydrogen type cation exchange resin is preferably used.
The alkali metal silicate and active silicic acid are preferably dissolved or dispersed in water before being added to the emulsion. The concentration of the alkali metal silicate and activated silicic acid aqueous solution is preferably 3 to 30% by mass, more preferably 5 to 25% by mass in terms of SiO 2 concentration.
　ケイ素アルコキシドとしては、例えば、テトラメトキシシラン、テトラエトキシシラン、テトラプロポキシシラン等のテトラアルキルシラン類が好ましく用いられる。
　また、シリカ原料とともに、他の金属酸化物等を混合することで、複合粒子を得ることも可能である。他の金属酸化物としては、二酸化チタン、酸化亜鉛、酸化セリウム、酸化銅、酸化鉄、酸化錫等が挙げられる。 As the silicon alkoxide, for example, tetraalkylsilanes such as tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane are preferably used.
It is also possible to obtain composite particles by mixing other metal oxides and the like with the silica raw material. Other metal oxides include titanium dioxide, zinc oxide, cerium oxide, copper oxide, iron oxide, tin oxide, and the like.
　第１のシリカ原料としては、上記したシリカ原料を単独で、又は２種以上を混合して用いられる。なかでも、第１のシリカ原料として、アルカリ金属ケイ酸塩水溶液、特にケイ酸ナトリウム水溶液を用いることが好ましい。 As the first silica raw material, the above-mentioned silica raw materials may be used alone or in a mixture of two or more. Among these, it is preferable to use an alkali metal silicate aqueous solution, particularly a sodium silicate aqueous solution, as the first silica raw material.
　第１のシリカ原料の水中油型エマルションへの添加は、酸性条件下で行うことが好ましい。酸性環境下でシリカ原料を添加することで、シリカ微粒子を発生させネットワークをつくることで１段目の被膜が形成される。反応温度は８０℃以下であることがエマルションの安定性維持のために好ましく、７０℃以下がより好ましく、６０℃以下がさらに好ましく、５０℃以下が特に好ましく、４０℃以下が最も好ましい。また、被膜の厚みを均一にするためにシリカ微粒子のネットワーク形成速度を制御する観点から、４℃以上であることが好ましく、１０℃以上がより好ましく、１５℃以上がさらに好ましく、２０℃以上が特に好ましく、２５℃以上が最も好ましい。 The addition of the first silica raw material to the oil-in-water emulsion is preferably carried out under acidic conditions. By adding a silica raw material in an acidic environment, fine silica particles are generated and a network is created to form the first layer of coating. The reaction temperature is preferably 80°C or lower to maintain stability of the emulsion, more preferably 70°C or lower, even more preferably 60°C or lower, particularly preferably 50°C or lower, and most preferably 40°C or lower. In addition, from the viewpoint of controlling the network formation rate of silica fine particles to make the thickness of the film uniform, the temperature is preferably 4°C or higher, more preferably 10°C or higher, even more preferably 15°C or higher, and even more preferably 20°C or higher. Particularly preferred, and most preferred is 25°C or higher.
　水中油型エマルションのｐＨは、被膜の厚さをより均一にし、得られる中空シリカのシリカシェル層をより緻密にするという観点から、３未満とすることがより好ましく、２．５以下がさらに好ましく、また、１以上であることがより好ましい。 The pH of the oil-in-water emulsion is more preferably less than 3, and even more preferably 2.5 or less, from the viewpoint of making the thickness of the film more uniform and making the silica shell layer of the resulting hollow silica more dense. , and more preferably 1 or more.
　水中油型エマルションのｐＨを酸性にするには、酸を添加することが挙げられる。
　酸としては、例えば、塩酸、硝酸、硫酸、酢酸、過塩素酸、臭化水素酸、トリクロロ酢酸、ジクロロ酢酸、メタンスルホン酸、ベンゼンスルホン酸等が挙げられる。 One way to make the pH of the oil-in-water emulsion acidic is to add an acid.
Examples of the acid include hydrochloric acid, nitric acid, sulfuric acid, acetic acid, perchloric acid, hydrobromic acid, trichloroacetic acid, dichloroacetic acid, methanesulfonic acid, and benzenesulfonic acid.
　第１のシリカ原料の添加では、第１のシリカ原料の添加量は、エマルション中に含まれる油相１００質量部に対して、第１のシリカ原料中のＳｉＯ２が１～５０質量部となるようにすることが好ましく、３～３０質量部がより好ましい。 In the addition of the first silica raw material, the amount of the first silica raw material added is 1 to 50 parts by mass of SiO 2 in the first silica raw material with respect to 100 parts by mass of the oil phase contained in the emulsion. The content is preferably 3 to 30 parts by mass, and more preferably 3 to 30 parts by mass.
　第１のシリカ原料の添加では、第１のシリカ原料を添加後、エマルションのｐＨを酸性に維持した状態で、１分以上保持することが好ましく、５分以上がより好ましく、１０分以上がさらに好ましい。 In addition of the first silica raw material, after adding the first silica raw material, it is preferable to maintain the pH of the emulsion in an acidic state for 1 minute or more, more preferably 5 minutes or more, and still more preferably 10 minutes or more. preferable.
　次に、第１のシリカ原料が添加されたエマルションのｐＨを３以上７以下（弱酸性から中性）で保持することが好ましい。これによって、第１のシリカ原料を油滴の表面に固定化できる。
　例えば、第１のシリカ原料を添加したエマルションに塩基を添加することで、エマルションのｐＨを３以上とする方法がある。 Next, it is preferable that the pH of the emulsion to which the first silica raw material is added is maintained at 3 or more and 7 or less (weakly acidic to neutral). This allows the first silica raw material to be immobilized on the surface of the oil droplet.
For example, there is a method of adjusting the pH of the emulsion to 3 or higher by adding a base to the emulsion to which the first silica raw material has been added.
　塩基としては、例えば、水酸化ナトリウム、水酸化カリウム等のアルカリ金属水酸化物、水酸化マグネシウム、水酸化カルシウム等のアルカリ土類金属水酸化物、アンモニア、アミン類等が挙げられる。
　あるいは陰イオン交換処理によりハロゲンイオン等の陰イオンを水酸化物イオンに交換する方法を用いてもよい。 Examples of the base include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkaline earth metal hydroxides such as magnesium hydroxide and calcium hydroxide, ammonia, and amines.
Alternatively, a method of exchanging anions such as halogen ions with hydroxide ions by anion exchange treatment may be used.
　塩基を添加する際は、第１のシリカ原料が添加されたエマルションを撹拌しながら塩基を徐々に添加して、エマルションのｐＨを徐々に上昇させることが好ましい。撹拌が弱かったり、多量の塩基を一度に投入したりすると、エマルションのｐＨが不均一になり、１層目の被膜の厚みが不均一になることがある。 When adding the base, it is preferable to gradually add the base while stirring the emulsion to which the first silica raw material has been added to gradually increase the pH of the emulsion. If stirring is weak or a large amount of base is added at once, the pH of the emulsion may become uneven and the thickness of the first layer may become uneven.
　エマルションは、撹拌しながら保持することが好ましい。この保持時間は、１０分以上であってよく、１時間以上が好ましく、４時間以上であってもよい。この保持温度は１００℃以下であることがエマルションの安定性維持のために好ましく、９５℃以下がより好ましく、９０℃以下がさらに好ましく、８５℃以下が特に好ましい。また、熟成を促進させるためには保持温度は、３５℃以上が好ましく、４０℃以上がより好ましく、４５℃以上が特に好ましい。 It is preferable to maintain the emulsion while stirring. This holding time may be 10 minutes or more, preferably 1 hour or more, and may be 4 hours or more. This holding temperature is preferably 100°C or lower in order to maintain the stability of the emulsion, more preferably 95°C or lower, even more preferably 90°C or lower, and particularly preferably 85°C or lower. Further, in order to promote ripening, the holding temperature is preferably 35°C or higher, more preferably 40°C or higher, and particularly preferably 45°C or higher.
〔２段目シェルの形成〕
　次に、アルカリ金属イオン存在下、エマルションに第２のシリカ原料を添加する。これによって、中空シリカ前駆体分散液が得られる。ここで、中空シリカ前駆体は、オイルコア－シリカシェル粒子となっている。 [Formation of second stage shell]
Next, a second silica raw material is added to the emulsion in the presence of alkali metal ions. This yields a hollow silica precursor dispersion. Here, the hollow silica precursor is an oil core-silica shell particle.
　第２のシリカ原料のエマルションへの添加は、アルカリ性条件下で行うことが好ましい。
　第１のシリカ原料の添加では、油滴への第１のシリカ原料の付着をより均一にするために、エマルションを一旦酸性とした後にｐＨを３以上７以下（弱酸性から中性）にする方法を用いている。この方法によって得られる１層目のシリカ層は多孔質であり、緻密性が不十分なため強度が低くなってしまう。第２のシリカ原料の添加において、エマルションをアルカリ性とすることで、先に得られた１層目のシリカ層上に、高密度な２層目のシリカ層を形成できる。 It is preferable that the second silica raw material is added to the emulsion under alkaline conditions.
In addition of the first silica raw material, in order to make the attachment of the first silica raw material to the oil droplets more uniform, the emulsion is made acidic and then the pH is adjusted from 3 to 7 (weakly acidic to neutral). method is used. The first silica layer obtained by this method is porous and has insufficient density, resulting in low strength. By making the emulsion alkaline in the addition of the second silica raw material, a high-density second silica layer can be formed on the previously obtained first silica layer.
　第２のシリカ原料を添加する際のエマルションのｐＨは、新しい微粒子の発生を抑えるために、８以上であることが好ましく、８．５以上がより好ましく、８．７以上がさらに好ましく、８．９以上が特に好ましく、９以上が最も好ましい。また、ｐＨが高すぎるとシリカの溶解度が大きくなるため、１３以下であることが好ましく、１２．５以下がよりに好ましく、１２以下がさらに好ましく、１１．５以下が特に好ましく、１１以下が最も好ましい。 The pH of the emulsion when adding the second silica raw material is preferably 8 or higher, more preferably 8.5 or higher, even more preferably 8.7 or higher, in order to suppress the generation of new fine particles. 9 or more is particularly preferred, and 9 or more is most preferred. Furthermore, if the pH is too high, the solubility of silica increases, so it is preferably 13 or less, more preferably 12.5 or less, even more preferably 12 or less, particularly preferably 11.5 or less, and most preferably 11 or less. preferable.
　水中油型エマルションのｐＨをアルカリ性にするには、塩基を添加することが挙げられる。塩基としては、上記したものと同様の化合物が用いられる。 One way to make the pH of the oil-in-water emulsion alkaline is to add a base. As the base, the same compounds as those mentioned above are used.
　第２のシリカ原料としては、上記した第１のシリカ原料と同様のものを単独で、又は２種以上を混合して用いられる。なかでも、第２のシリカ原料の添加では、ケイ酸ナトリウム水溶液及び活性ケイ酸水溶液の少なくとも一方が好ましく用いられる。
　エマルションをアルカリ性条件下で第２のシリカ原料を添加する際には、第２のシリカ原料と同時にアルカリ金属水酸化物を添加する方法を用いてもよい。また、第２のシリカ原料にアルカリ金属ケイ酸塩としてケイ酸ナトリウムを用いる方法でもよい。この場合、第１のシリカ原料の添加後にｐＨを５以上とした弱酸性のエマルションに、アルカリ成分であるケイ酸ナトリウムを添加するため、第２のシリカ原料を添加しながらエマルションのｐＨをアルカリ性に保持できる。また、アルカリ金属イオンがエマルション中に存在するようになる。 As the second silica raw material, the same materials as the above-described first silica raw material may be used alone or in a mixture of two or more. Among these, at least one of an aqueous sodium silicate solution and an aqueous activated silicic acid solution is preferably used in the addition of the second silica raw material.
When adding the second silica raw material to the emulsion under alkaline conditions, a method may be used in which the alkali metal hydroxide is added simultaneously with the second silica raw material. Alternatively, a method may be adopted in which sodium silicate is used as the alkali metal silicate in the second silica raw material. In this case, the pH of the emulsion is made alkaline while adding the second silica raw material to add sodium silicate, which is an alkaline component, to the slightly acidic emulsion whose pH is set to 5 or higher after the addition of the first silica raw material. Can be retained. Also, alkali metal ions become present in the emulsion.
　なお、第２のシリカ原料にケイ酸ナトリウム水溶液を用いる場合などで、ｐＨが上がりすぎてしまう場合は、ｐＨを調整するために酸を加えてもよい。ここで用いる酸には、第１のシリカ原料を添加する時と同じ酸を用いてもよい。 Note that if the pH increases too much, such as when an aqueous sodium silicate solution is used as the second silica raw material, an acid may be added to adjust the pH. The acid used here may be the same as when adding the first silica raw material.
　第２のシリカ原料の添加はアルカリ金属イオンの存在下で行うことが好ましい。このアルカリ金属イオンは、第１のシリカ原料由来、第２のシリカ原料由来、ｐＨ調整のために加えた塩基由来であってよく、エマルションへの添加剤の添加等によっても配合が可能である。例えば、第１のシリカ原料及び第２のシリカ原料の少なくとも一方に、アルカリ金属ケイ酸塩を用いる場合である。また、エマルションの添加剤に、アルカリ金属のハロゲン化物、硫酸塩、硝酸塩、脂肪酸塩等を用いる場合である。 It is preferable that the second silica raw material is added in the presence of alkali metal ions. This alkali metal ion may be derived from the first silica raw material, the second silica raw material, or a base added for pH adjustment, and can also be blended by adding additives to the emulsion. For example, this is the case where an alkali metal silicate is used as at least one of the first silica raw material and the second silica raw material. This is also the case where alkali metal halides, sulfates, nitrates, fatty acid salts, etc. are used as additives for the emulsion.
　第２のシリカ原料の添加は、例えば、第１のシリカ原料の添加後のエマルションに、ケイ酸ナトリウム水溶液及び活性ケイ酸水溶液のうち一方を添加してもよく、両方を添加してもよい。両方を添加する場合は、ケイ酸ナトリウム水溶液及び活性ケイ酸水溶液を一括して添加してもよいし、順番に添加してもよい。 The second silica raw material may be added, for example, by adding one or both of a sodium silicate aqueous solution and an activated silicic acid aqueous solution to the emulsion after addition of the first silica raw material. When both are added, the sodium silicate aqueous solution and the activated silicic acid aqueous solution may be added all at once, or may be added in order.
　例えば、第２のシリカ原料の添加は、ｐＨ調整をしながら、１層目のシリカ層上へのシリカ原料の付着を促進するために、ケイ酸ナトリウム水溶液を添加する工程と、活性ケイ酸水溶液を添加する工程とを、１回又は２回以上繰り返して行える。 For example, the addition of the second silica raw material includes a step of adding a sodium silicate aqueous solution to promote adhesion of the silica raw material onto the first silica layer while adjusting the pH, and an activated silicate aqueous solution. The step of adding can be repeated once or twice or more.
　第２のシリカ原料は、１層目のシリカ層上へのシリカ原料の付着を促進するために、加熱されたエマルションに添加することが好ましい。加熱温度は、新しい微粒子の発生を抑えるため、３０℃以上が好ましく、３５℃以上がより好ましく、４０℃以上がさらに好ましく、４５℃以上が特に好ましく、５０℃以上が最も好ましい。温度が高くなるとシリカの溶解度が高くなるため、１００℃以下が好ましく、９５℃以下がより好ましく、９０℃以下がさらに好ましく、８５℃以下が特に好ましく、８０℃以下が最も好ましい。加熱されたエマルションを用いた場合、第２のシリカ原料の添加後は、生成したエマルションを室温（約２３℃）まで徐冷することが好ましい。すなわち、加熱温度は、３０～１００℃の範囲が好ましい。 The second silica raw material is preferably added to the heated emulsion in order to promote adhesion of the silica raw material onto the first silica layer. The heating temperature is preferably 30°C or higher, more preferably 35°C or higher, even more preferably 40°C or higher, particularly preferably 45°C or higher, and most preferably 50°C or higher, in order to suppress the generation of new fine particles. Since the solubility of silica increases as the temperature increases, the temperature is preferably 100°C or lower, more preferably 95°C or lower, even more preferably 90°C or lower, particularly preferably 85°C or lower, and most preferably 80°C or lower. When a heated emulsion is used, it is preferable to gradually cool the generated emulsion to room temperature (about 23° C.) after adding the second silica raw material. That is, the heating temperature is preferably in the range of 30 to 100°C.
　第２のシリカ原料の添加では、第２のシリカ原料の添加量は、油相１００質量部に対して、第２のシリカ原料中のＳｉＯ２が２０～５００質量部となるように調整されるのが好ましく、４０～３００質量部となるように調整されるのがより好ましい。
　第２のシリカ原料の添加では、第２のシリカ原料を添加後にエマルションのｐＨをアルカリ性に維持した状態で、１０分以上保持することが好ましい。 In addition of the second silica raw material, the amount of the second silica raw material added is adjusted such that SiO 2 in the second silica raw material is 20 to 500 parts by mass with respect to 100 parts by mass of the oil phase. The amount is preferably adjusted to 40 to 300 parts by mass.
When adding the second silica raw material, it is preferable to maintain the pH of the emulsion at an alkaline state for 10 minutes or more after adding the second silica raw material.
　第１のシリカ原料の添加及び第２のシリカ原料の添加を通して、第１のシリカ原料及び第２のシリカ原料の添加量の合計量は、油相１００質量部に対して、第１のシリカ原料中のＳｉＯ２と第２のシリカ原料中のＳｉＯ２の合計が３０～５００質量部となるように調整されるのが好ましく、５０～３００質量部となるように調整されるのがより好ましい。 Through the addition of the first silica raw material and the addition of the second silica raw material, the total amount of the first silica raw material and the second silica raw material added is determined based on the amount of the first silica raw material added to 100 parts by mass of the oil phase. The total amount of SiO 2 in the second silica raw material and SiO 2 in the second silica raw material is preferably adjusted to be 30 to 500 parts by mass, more preferably 50 to 300 parts by mass.
　本発明のシリカシェル層は主としてシリカより構成されるが、屈折率調整など、必要に応じてＴｉやＺｒなどの他の金属成分を含有させてもよい。他の金属成分を含有させる方法は特に限定されないが、例えばシリカ原料を添加する工程で金属ゾル液や金属塩水溶液を同時に添加するなどの方法が用いられる。 The silica shell layer of the present invention is mainly composed of silica, but may contain other metal components such as Ti and Zr as necessary for adjusting the refractive index. The method of incorporating other metal components is not particularly limited, but for example, a method of adding a metal sol solution or a metal salt aqueous solution at the same time in the step of adding the silica raw material can be used.
　上記のようにして中空シリカ前駆体分散液が得られる。 A hollow silica precursor dispersion is obtained as described above.
　中空シリカ前駆体分散液から中空シリカ前駆体を得る方法としては、例えば、分散液をろ過する方法、加熱して水相を除去する方法、沈降分離もしくは遠心分離により前駆体を分離する方法等がある。
　一例としては、０．１μｍ～５μｍ程度のフィルターを用いて分散液をろ過し、ろ別された中空シリカ前駆体を乾燥する方法がある。 Examples of methods for obtaining a hollow silica precursor from a hollow silica precursor dispersion include a method of filtering the dispersion, a method of heating to remove the aqueous phase, and a method of separating the precursor by sedimentation or centrifugation. be.
One example is a method in which the dispersion is filtered using a filter of about 0.1 μm to 5 μm, and the filtered hollow silica precursor is dried.
　また必要に応じて、得られた中空シリカ前駆体を、水や酸、アルカリ、有機溶剤等で洗浄してもよい。 Further, if necessary, the obtained hollow silica precursor may be washed with water, acid, alkali, organic solvent, etc.
〔中空シリカ前駆体の熱処理〕
　そして、中空シリカ前駆体からオイルコアを除去して熱処理する。オイルコアを除去する方法としては、例えば、中空シリカ前駆体を焼成しオイルを燃焼分解する方法、乾燥によりオイルを揮発させる方法、適切な添加剤を加えてオイルを分解させる方法、有機溶媒等を用いてオイルを抽出する方法等がある。中でも、オイルの残留物が少ない中空シリカ前駆体を焼成してオイルを燃焼分解する方法が好ましい。 [Heat treatment of hollow silica precursor]
Then, the oil core is removed from the hollow silica precursor and heat treated. Methods for removing the oil core include, for example, burning a hollow silica precursor to burn and decompose the oil, evaporating the oil by drying, adding appropriate additives to decomposing the oil, using organic solvents, etc. There are several methods of extracting oil. Among these, a method of burning and decomposing oil by firing a hollow silica precursor with little oil residue is preferred.
　以下、中空シリカ前駆体を焼成してオイルコアを除去し、熱処理する方法を例に説明する。
　中空シリカ前駆体を焼成することによりオイルコアを除去し、中空シリカ粒子を得る方法では、少なくとも２段階の異なる温度で熱処理することが好ましい。１段目の熱処理によりオイルコアを除去し、２段目の熱処理で中空シリカ粒子のシェル層の緻密化を行う。 Hereinafter, a method of firing a hollow silica precursor to remove an oil core and heat-treating the hollow silica precursor will be described as an example.
In the method of removing the oil core and obtaining hollow silica particles by firing a hollow silica precursor, it is preferable to perform heat treatment at at least two different temperatures. The oil core is removed in the first heat treatment, and the shell layer of the hollow silica particles is densified in the second heat treatment.
　１段目の熱処理では、オイルコアと界面活性剤の有機成分を除去する。中空シリカ前駆体内のオイルを熱分解する必要があるため、１００℃以上で行うのが好ましく、２００℃以上がより好ましく、３００℃以上が最も好ましい。１段目の熱処理が高温過ぎると、シリカシェルの緻密化が進み内部の有機成分の除去が難しくなるため、７００℃未満で行うのが好ましく、５５０℃以下が好ましく、５３０℃以下がより好ましく、５２０℃以下がさらに好ましく、５１０℃以下が特に好ましく、５００℃以下が最も好ましい。すなわち、１００℃以上７００℃未満の範囲で１段目の熱処理を行うのが好ましい。１段目の熱処理は、１回で行ってもよいし、複数回行ってもよい。１段目の熱処理時間は、３０分以上が好ましく、１時間以上が好ましく、２時間以上がより好ましく、また、４８時間以下が好ましく、２４時間以下がより好ましく、１２時間以下がより好ましい。すなわち、１段目の熱処理時間は、３０分～４８時間の範囲が好ましい。 In the first heat treatment, the organic components of the oil core and surfactant are removed. Since it is necessary to thermally decompose the oil in the hollow silica precursor, the temperature is preferably 100°C or higher, more preferably 200°C or higher, and most preferably 300°C or higher. If the first stage heat treatment is performed at too high a temperature, the silica shell will become denser and it will be difficult to remove the organic components inside, so it is preferably carried out at a temperature of less than 700°C, preferably 550°C or less, more preferably 530°C or less, The temperature is more preferably 520°C or lower, particularly preferably 510°C or lower, and most preferably 500°C or lower. That is, it is preferable to perform the first heat treatment at a temperature of 100°C or more and less than 700°C. The first stage heat treatment may be performed once or multiple times. The first heat treatment time is preferably 30 minutes or more, preferably 1 hour or more, more preferably 2 hours or more, and preferably 48 hours or less, more preferably 24 hours or less, and even more preferably 12 hours or less. That is, the first stage heat treatment time is preferably in the range of 30 minutes to 48 hours.
　そして、２段目の熱処理では、中空シリカ粒子を焼しめ、シェルの緻密化を行う。また、２段目の熱処理により粒子表面のシラノール基を減少させ、誘電正接を低下できる。２段目の焼成温度は１段目の熱処理温度よりも高い温度で行うことが好ましい。 Then, in the second stage of heat treatment, the hollow silica particles are baked to densify the shell. In addition, the second heat treatment reduces the number of silanol groups on the particle surface and lowers the dielectric loss tangent. The second stage firing temperature is preferably higher than the first stage heat treatment temperature.
　２段目の熱処理を静置法で行う際は、７００℃以上で行うのが好ましく、８００℃以上がより好ましく、９００℃以上がさらに好ましく、１０００℃以上が最も好ましい。また、温度が高くなり過ぎると、アモルファスシリカの結晶化が起こって比誘電率が高くなるため、１２００℃以下で行うのが好ましく、１１５０℃以下がより好ましく、１１００℃以下が最も好ましい。すなわち、７００～１２００℃の範囲で２段目の熱処理を行うのが好ましい。なお、２段目の熱処理温度は、１段目の熱処理温度よりも２００℃以上高いことが好ましく、２００～８００℃高いことがより好ましく、４００～７００℃高いことがさらに好ましい。２段目の熱処理は、１回で行ってもよいし、複数回行ってもよい。熱処理時間は１０分以上が好ましく、３０分以上がより好ましく、また、２４時間以下が好ましく、１２時間以下がより好ましく、６時間以下が最も好ましい。すなわち、２段目の熱処理時間は、１０分～２４時間の範囲が好ましい。 When performing the second heat treatment by a standing method, it is preferably carried out at a temperature of 700°C or higher, more preferably 800°C or higher, even more preferably 900°C or higher, and most preferably 1000°C or higher. Furthermore, if the temperature becomes too high, crystallization of amorphous silica occurs and the dielectric constant increases, so it is preferably carried out at 1200°C or lower, more preferably 1150°C or lower, and most preferably 1100°C or lower. That is, it is preferable to perform the second heat treatment at a temperature in the range of 700 to 1200°C. The second stage heat treatment temperature is preferably 200°C or more higher than the first stage heat treatment temperature, more preferably 200 to 800°C higher, and even more preferably 400 to 700°C higher. The second stage heat treatment may be performed once or multiple times. The heat treatment time is preferably 10 minutes or more, more preferably 30 minutes or more, preferably 24 hours or less, more preferably 12 hours or less, and most preferably 6 hours or less. That is, the second heat treatment time is preferably in the range of 10 minutes to 24 hours.
　また、２段目の熱処理は噴霧燃焼法を用いてもよい。その際の火炎温度は１０００℃以上が好ましく、１２００℃以上が好ましく、１４００℃以上が最も好ましい。また、火炎温度は２０００℃以下が好ましく、１８００℃以下がより好ましく、１６００℃以下が最も好ましい。すなわち、２段目の熱処理に噴霧燃焼法を用いる場合、火炎温度は１０００～２０００℃の範囲が好ましい。 Additionally, a spray combustion method may be used for the second stage heat treatment. The flame temperature at that time is preferably 1000°C or higher, preferably 1200°C or higher, and most preferably 1400°C or higher. Further, the flame temperature is preferably 2000°C or less, more preferably 1800°C or less, and most preferably 1600°C or less. That is, when the spray combustion method is used for the second stage heat treatment, the flame temperature is preferably in the range of 1000 to 2000°C.
　なお、１段目の焼成後、２段目の熱処理を行う前に中空シリカ前駆体を室温に戻してもよいし、１段目の焼成温度を維持した状態から２段目の熱処理温度に昇温してもよい。 Note that after the first stage firing, the hollow silica precursor may be returned to room temperature before the second stage heat treatment, or the hollow silica precursor may be raised to the second stage heat treatment temperature from a state where the first stage firing temperature is maintained. You can warm it up.
　上記工程により得られた中空シリカ粒子は、乾燥や焼成の工程により凝集していることがあるため、取り扱いやすい凝集径にするために解砕してもよいが、本発明ではそのまま溶媒と混合してシリカ粒子分散液を得られる。
　なお、解砕の方法としては、例えば、乳鉢を使う方法、乾式あるいは湿式のボールミルを使う方法、振とう式篩を使う方法、ピンミル、カッターミル、ハンマーミル、ナイフミル、ローラーミル、ジェットミルなどの解砕機を使う方法等が挙げられる。 Since the hollow silica particles obtained in the above process may be aggregated due to the drying or firing process, they may be crushed to make the aggregate diameter easier to handle, but in the present invention, they may be crushed as is by mixing with the solvent. A silica particle dispersion can be obtained.
Examples of crushing methods include a mortar, a dry or wet ball mill, a shaking sieve, a pin mill, a cutter mill, a hammer mill, a knife mill, a roller mill, and a jet mill. Examples include a method using a crusher.
　このようにして本発明のシリカ粒子分散液に用いる前記した中空シリカ粒子が得られる。 In this way, the above-described hollow silica particles used in the silica particle dispersion of the present invention are obtained.
（シリカ粒子分散液の調製）
　得られた中空シリカ粒子は、溶媒と混合し、シリカ粒子分散液を得る。本発明のシリカ粒子分散液の製造方法では、溶媒と平均粒子径が０．２～１０μｍの範囲の中空シリカ粒子の粉末とを混合し、混合液を分散処理し、分級して中空シリカ粒子の凝集物を除去することを含む。
　溶媒の種類や使用量、中空シリカ粒子の物性や使用量等は前述のとおりである。 (Preparation of silica particle dispersion)
The obtained hollow silica particles are mixed with a solvent to obtain a silica particle dispersion. In the method for producing a silica particle dispersion of the present invention, a solvent and powder of hollow silica particles having an average particle diameter in the range of 0.2 to 10 μm are mixed, the mixed liquid is subjected to a dispersion treatment, and classified to form hollow silica particles. including removing aggregates.
The type and amount of the solvent used, the physical properties of the hollow silica particles, the amount used, etc. are as described above.
　中空シリカ粒子の粉末は、シリカ粒子分散液中に５～８０体積％の割合で混合するのが好ましい。中空シリカ粒子の割合が少なすぎると後の濃縮工程の生産性が落ち、また多過ぎるとシリカ粒子分散液の粘度が上がり過ぎて分散処理の生産性が落ちることがあるので、５～８０体積％の範囲が好ましい。中空シリカ粒子の使用量は、１０体積％以上であるのがより好ましく、２０体積％以上がさらに好ましく、また、６０体積％以下であるのがより好ましく、５０体積％以下がさらに好ましい。 The hollow silica particle powder is preferably mixed in the silica particle dispersion at a ratio of 5 to 80% by volume. If the proportion of hollow silica particles is too small, the productivity of the subsequent concentration step will decrease, and if it is too large, the viscosity of the silica particle dispersion may increase too much and the productivity of dispersion treatment may decrease, so it should be 5 to 80% by volume. A range of is preferred. The amount of hollow silica particles used is more preferably 10% by volume or more, even more preferably 20% by volume or more, more preferably 60% by volume or less, even more preferably 50% by volume or less.
　溶媒と中空シリカ粒子を含む混合液の分散処理は、顔料分散等で使用される分散装置を使用できる。例えば、ディスパー、ホモミキサー、プラネタリーミキサー等のミキサー類、ホモジナイザー（エム・テクニック社製「クレアミックス」、ＰＲＩＭＩＸ社「フィルミックス」等、シルバーソン社製「アブラミックス」等）類、ペイントコンディショナー（レッドデビル社製）、コロイドミル（ＰＵＣ社製「ＰＵＣコロイドミル」、ＩＫＡ社製「コロイドミルＭＫ」）類、コーンミル（ＩＫＡ社製「コーンミルＭＫＯ」等）、ボールミル、サンドミル（シンマルエンタープライゼス社製「ダイノミル」等）、アトライター、パールミル（アイリッヒ社製「ＤＣＰミル」等）、コボールミル等のメディア型分散機、湿式ジェットミル（ジーナス社製「ジーナスＰＹ」、スギノマシン社製「スターバースト」、ナノマイザー社製「ナノマイザー」等）、エム・テクニック社製「クレアＳＳ－５」、奈良機械社製「ＭＩＣＲＯＳ」等のメディアレス分散機、その他ロールミル、ニーダー等が挙げられる。その中でも、粉砕メディア（ボール、ビーズ等）を用いないものが望ましい。粉砕メディアを用いると、摩耗したメディアのコンタミネーションが懸念されるためである。具体的には、湿式ジェットミル（ジーナス社製「ジーナスＰＹ」、スギノマシン社製「スターバースト」、ナノマイザー社製「ナノマイザー」等）、エム・テクニック社製「クレアＳＳ－５」、奈良機械社製「ＭＩＣＲＯＳ」等のメディアレス分散機が望ましい。 A dispersion device used for pigment dispersion, etc. can be used for dispersion of a liquid mixture containing a solvent and hollow silica particles. For example, mixers such as dispers, homomixers, and planetary mixers, homogenizers (M Technique's "Clearmix", PRIMIX's "Filmix", etc., Silverson's "Abramix", etc.), paint conditioners ( Red Devil), colloid mills (PUC Colloid Mill, IKA Colloid Mill MK), corn mills (IKA Corn Mill MKO, etc.), ball mills, sand mills (Shinmaru Enterprises) "Dyno Mill" manufactured by Manufacturer Co., Ltd.), attritor, pearl mill ("DCP Mill" manufactured by Eirich Co., Ltd., etc.), media-type dispersion machines such as Koboru Mill, wet jet mill ("Ginas PY" manufactured by Genus Co., Ltd., "Starburst" manufactured by Sugino Machine Co., Ltd.) , "Nanomizer" manufactured by Nanomizer Co., Ltd.), "Claire SS-5" manufactured by M Techniques, "MICROS" manufactured by Nara Kikai Co., Ltd., and other medialess dispersion machines such as roll mills, kneaders, etc. Among these, those that do not use grinding media (balls, beads, etc.) are desirable. This is because if grinding media is used, there is a concern about contamination of worn media. Specifically, wet jet mills (Genus PY, manufactured by Genus, Starburst, manufactured by Sugino Machine, Nanomizer, manufactured by Nanomizer, etc.), Clair SS-5, manufactured by M Technique, Nara Kikai A medialess dispersion machine such as "MICROS" manufactured by Manufacturer Co., Ltd. is preferable.
　また、分散処理時の温度は、０～１００℃で行うのが好ましい。ここで分散処理時の温度は、処理前後の温度範囲のことを指す。前記温度範囲で分散処理することで溶媒の粘度が適度に保たれ、生産性が保たれ、また溶媒の蒸発を抑えて固形分を容易に制御できる。処理温度は、５℃以上であるのがより好ましく、１０℃以上がさらに好ましく、また、９０℃以下であるのがより好ましく、８０℃以下がさらに好ましい。 Furthermore, the temperature during the dispersion treatment is preferably 0 to 100°C. The temperature during the dispersion treatment here refers to the temperature range before and after the treatment. By performing the dispersion treatment in the above temperature range, the viscosity of the solvent can be maintained at an appropriate level, productivity can be maintained, and the solid content can be easily controlled by suppressing evaporation of the solvent. The treatment temperature is more preferably 5°C or higher, even more preferably 10°C or higher, more preferably 90°C or lower, and even more preferably 80°C or lower.
　分散処理の時間としては、中空シリカ粒子の中空構造を破壊しないよう使用する分散装置に応じて適宜設定すればよいが、０．５～６０分で行うのが好ましく、０．５～１０分がより好ましく、０．５～５分がさらに好ましい。 The time for the dispersion treatment may be set appropriately depending on the dispersion device used so as not to destroy the hollow structure of the hollow silica particles, but it is preferably carried out for 0.5 to 60 minutes, and 0.5 to 10 minutes. More preferably, 0.5 to 5 minutes is even more preferable.
　その後、分散処理でも分散しきれずに残った中空シリカ粒子の凝集物を湿式分級する。湿式分級は篩や遠心力による分級等が挙げられる。篩を用いる場合、目開き１００μｍ以下の篩により分級するのが好ましい。篩としては、例えば、電鋳ふるいのような緻密な格子状の構造を持つ金属を用いるのが好ましい。 Thereafter, aggregates of hollow silica particles that remained after being unable to be dispersed even during the dispersion treatment are wet classified. Examples of wet classification include classification using a sieve or centrifugal force. When using a sieve, it is preferable to classify using a sieve with an opening of 100 μm or less. As the sieve, it is preferable to use a metal having a dense lattice structure, such as an electroformed sieve.
　篩の目開きは１００μｍ以下であるのが好ましく、７５μｍ以下がより好ましく、５０μｍ以下がさらに好ましく、３５μｍ以下が特に好ましい。また、篩の目開きの下限は、０．２μｍ以上であるのが好ましく、０．５μｍ以上がより好ましく、１μｍ以上がさらに好ましい。すなわち、篩の目開きは０．２～１００μｍの範囲が好ましい。 The opening of the sieve is preferably 100 μm or less, more preferably 75 μm or less, even more preferably 50 μm or less, and particularly preferably 35 μm or less. Further, the lower limit of the opening of the sieve is preferably 0.2 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more. That is, the opening of the sieve is preferably in the range of 0.2 to 100 μm.
　その後、必要に応じて希釈あるいは濃縮し、適当な濃度に調整してもよい。濃縮の方法としては、気化濃縮、固液分離等が挙げられる。 Thereafter, it may be diluted or concentrated as necessary to adjust to an appropriate concentration. Examples of the concentration method include vaporization concentration, solid-liquid separation, and the like.
　なお、本発明のシリカ粒子分散液の製造方法では、溶媒と中空シリカ粒子の混合液にシランカップリング剤を添加してもよい。シランカップリング剤としては前述のシランカップリング剤が例示される。 Note that in the method for producing a silica particle dispersion of the present invention, a silane coupling agent may be added to the mixture of the solvent and hollow silica particles. Examples of the silane coupling agent include the aforementioned silane coupling agents.
＜樹脂組成物＞
　本発明のシリカ粒子分散液は、樹脂と混合し、樹脂組成物として利用できる。樹脂組成物中、中空シリカ粒子を５～７０質量％の範囲で含むことが好ましく、１０～５０質量％がより好ましい。 <Resin composition>
The silica particle dispersion of the present invention can be mixed with a resin and used as a resin composition. The resin composition preferably contains hollow silica particles in an amount of 5 to 70% by mass, more preferably 10 to 50% by mass.
　樹脂としては、エポキシ樹脂、シリコーン樹脂、フェノール樹脂、メラミン樹脂、ユリア樹脂、不飽和ポリエステル、フッ素樹脂、ポリイミド、ポリアミドイミド、ポリエーテルイミド等のポリアミド；ポリブチレンテレフタレート、ポリエチレンテレフタレート等のポリエステル；ポリフェニレンスルフィド、芳香族ポリエステル、ポリスルホン、液晶ポリマー、ポリエーテルスルホン、ポリカーボネート、マレイミド変成樹脂、ＡＢＳ樹脂、ＡＡＳ（アクリロニトリルーアクリルゴム・スチレン）樹脂、ＡＥＳ（アクリロニトリル・エチレン・プロピレン・ジエンゴム－スチレン）樹脂、ポリテトラフルオロエチレン（ＰＴＦＥ）、テトラフルオロエチレン－パーフルオロアルキルビニルエーテル共重合体（ＰＦＡ）、テトラフルオロエチレン－ヘキサフルオロプロピレン共重合体（ＦＥＰ）、テトラフルオロエチレン－エチレン共重合体（ＥＴＦＥ）の１種または２種以上等を使用できる。樹脂組成物における誘電正接は樹脂の特性にも依存するので、これらを考慮して使用する樹脂を選択すればよい。 Examples of resins include epoxy resins, silicone resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, fluororesins, polyamides such as polyimide, polyamideimide, and polyetherimide; polyesters such as polybutylene terephthalate and polyethylene terephthalate; polyphenylene sulfide , aromatic polyester, polysulfone, liquid crystal polymer, polyether sulfone, polycarbonate, maleimide modified resin, ABS resin, AAS (acrylonitrile-acrylic rubber-styrene) resin, AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resin, polytetra One of fluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), or Two or more types can be used. Since the dielectric loss tangent in a resin composition also depends on the characteristics of the resin, the resin to be used may be selected taking these into consideration.
　樹脂組成物は、上記樹脂以外に任意の成分を含んでいてもよい。任意の成分としては、例えば、分散助剤、界面活性剤、シリカ以外のフィラー等が挙げられる。 The resin composition may contain any component other than the above resin. Examples of optional components include dispersion aids, surfactants, fillers other than silica, and the like.
　なお、本発明の樹脂組成物を用いて樹脂フィルムを作製したとき、その比誘電率が、周波数１０ＧＨｚにおいて２．０～３．５であるのが好ましく、下限は、２．２以上がより好ましく、２．３以上がさらに好ましく、また上限は、３．２以下がより好ましく、３．０以下がさらに好ましい。樹脂フィルムの周波数１０ＧＨｚでの比誘電率が前記範囲であると、電気特性に優れるので電子機器や通信機器等への利用が期待できる。 Note that when a resin film is produced using the resin composition of the present invention, the dielectric constant thereof is preferably 2.0 to 3.5 at a frequency of 10 GHz, and the lower limit is more preferably 2.2 or more. , more preferably 2.3 or more, and the upper limit is more preferably 3.2 or less, even more preferably 3.0 or less. When the dielectric constant of the resin film at a frequency of 10 GHz is within the above range, it has excellent electrical properties and can be expected to be used in electronic equipment, communication equipment, etc.
　また、樹脂フィルムの誘電正接は、周波数１０ＧＨｚにおいて０．０１以下であるのが好ましく、０．００８以下がより好ましく、０．００６５以下がさらに好ましい。樹脂フィルムの周波数１０ＧＨｚでの誘電正接が前記範囲であると、電気特性に優れるので電子機器や通信機器等への利用が期待できる。誘電正接が小さいほど、回路の伝送損失が抑えられるため、下限値は特に限定されない。 Furthermore, the dielectric loss tangent of the resin film is preferably 0.01 or less at a frequency of 10 GHz, more preferably 0.008 or less, and even more preferably 0.0065 or less. When the dielectric loss tangent of the resin film at a frequency of 10 GHz is within the above range, it has excellent electrical properties and can be expected to be used in electronic equipment, communication equipment, etc. The smaller the dielectric loss tangent, the more suppressed the transmission loss of the circuit, so the lower limit is not particularly limited.
　誘電正接は、スプリットポスト誘電体共振器（ＳＰＤＲ）（例えば、Ａｇｉｌｅｎｔ　Ｔｅｃｈｎｏｌｏｇｉｅｓ社製）を用いて測定できる。 The dielectric loss tangent can be measured using a split post dielectric resonator (SPDR) (eg, manufactured by Agilent Technologies).
　また、上記樹脂フィルムの平均線膨張率が、１０～５０ｐｐｍ／℃であるのが好ましい。平均線膨張率が前記範囲であると、基材として広く使用される銅箔の熱膨張係数に近い範囲であるので、電気特性に優れる。平均線膨張率は、１２ｐｐｍ／℃以上であるのがより好ましく、１５ｐｐｍ／℃以上がさらに好ましく、また４０ｐｐｍ／℃以下であるのがより好ましく、３０ｐｐｍ／℃以下がさらに好ましい。 Further, it is preferable that the resin film has an average linear expansion coefficient of 10 to 50 ppm/°C. When the average coefficient of linear expansion is within the above range, it is close to the coefficient of thermal expansion of copper foil, which is widely used as a base material, and therefore has excellent electrical properties. The average coefficient of linear expansion is more preferably 12 ppm/°C or higher, even more preferably 15 ppm/°C or higher, more preferably 40 ppm/°C or lower, even more preferably 30 ppm/°C or lower.
　平均線膨張率は、熱機械分析装置（例えば、島津製作所社製、「ＴＭＡ－６０」）を使用して、上記樹脂フィルムを荷重５Ｎ、昇温速度２℃／ｍｉｎで加熱し、３０℃から１５０℃までのサンプルの寸法変化を測定し、平均を算出することで求められる。 The average coefficient of linear expansion is determined by heating the above resin film at a load of 5N and a temperature increase rate of 2°C/min from 30°C using a thermomechanical analyzer (for example, "TMA-60" manufactured by Shimadzu Corporation). It is determined by measuring the dimensional change of a sample up to 150°C and calculating the average.
　本発明のシリカ粒子分散液は、各種充填材として使用でき、特にパソコン、ノートパソコン、デジタルカメラ等の電子機器や、スマートフォン、ゲーム機等の通信機器等に用いられる電子基板の作製に用いられる樹脂組成物の充填材として好適に使用できる。具体的には、本発明のシリカ粒子分散液は、低誘電率化、低伝送損失化、低吸湿化、剥離強度向上のために、樹脂組成物、プリプレグ、金属箔張積層板、プリント配線板、樹脂シート、接着層、接着フィルム、ソルダーレジスト、バンプリフロー用、再配線絶縁層、ダイボンド材、封止材、アンダーフィル、モールドアンダーフィルおよび積層インダクタ等への応用も期待される。 The silica particle dispersion of the present invention can be used as a variety of fillers, and is particularly used as a resin for producing electronic substrates used in electronic devices such as personal computers, notebook computers, and digital cameras, and communication devices such as smartphones and game consoles. It can be suitably used as a filler in compositions. Specifically, the silica particle dispersion of the present invention can be used in resin compositions, prepregs, metal foil-clad laminates, and printed wiring boards in order to reduce dielectric constant, reduce transmission loss, reduce moisture absorption, and improve peel strength. It is also expected to be applied to resin sheets, adhesive layers, adhesive films, solder resists, bump reflow applications, rewiring insulating layers, die bonding materials, encapsulants, underfills, mold underfills, and laminated inductors.
　以下、本発明を実施例により詳しく説明するが、本発明はこれらに限定されるものではない。以下の説明において、共通する成分は同じものを用いている。
　また、例１～１０は実施例であり、例１１～１３は比較例である。 EXAMPLES Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited thereto. In the following description, the same components are used in common.
Further, Examples 1 to 10 are examples, and Examples 11 to 13 are comparative examples.
＜試験例１＞
　試験例１では、中空シリカ粒子の作製及び得られた中空シリカ粒子を用いたシリカ粒子分散液の作製を行った。 <Test Example 1>
In Test Example 1, hollow silica particles were prepared and a silica particle dispersion liquid was prepared using the obtained hollow silica particles.
（例１）
「エマルションの作製」
　純水１２５０ｇにＥＯ－ＰＯ－ＥＯブロックコポリマー（ＡＤＥＫＡ社製プルロニックＦ６８）を４ｇ添加し溶解するまで撹拌した。この水溶液にソルビタン酸モノオレート（三洋化成社製イオネットＳ－８０）４ｇを溶解したｎ－デカン４２ｇを加え、ＩＫＡ社製ホモジナイザーを使って液全体が均一になるまで撹拌し、粗エマルションを作製した。
　この粗エマルションを、高圧乳化機（エスエムテー社製ＬＡＢ１０００）を使い、圧力５０ｂａｒで乳化を行い、エマルション径が１μｍの微細エマルションを作製した。 (Example 1)
"Preparation of emulsion"
4 g of EO-PO-EO block copolymer (Pluronic F68 manufactured by ADEKA) was added to 1250 g of pure water and stirred until dissolved. To this aqueous solution was added 42 g of n-decane in which 4 g of sorbitan acid monooleate (Ionet S-80, manufactured by Sanyo Chemical Co., Ltd.) was dissolved, and the mixture was stirred using an IKA homogenizer until the entire liquid became homogeneous to prepare a crude emulsion.
This rough emulsion was emulsified at a pressure of 50 bar using a high-pressure emulsifier (LAB1000, manufactured by SMT Co., Ltd.) to produce a fine emulsion with an emulsion diameter of 1 μm.
「乳化液エージング」
　得られた微細エマルションを４０℃で１２時間静置することで、エージング後エマルションを得た。 "Emulsion aging"
The resulting fine emulsion was allowed to stand at 40° C. for 12 hours to obtain an aged emulsion.
「１段目シェル形成」
　得られたエージング後エマルション１３００ｇに、ｐＨが２となるよう、希釈したケイ酸ナトリウム水溶液（ＳｉＯ２濃度１０．４質量％、Ｎａ２Ｏ濃度３．６質量％）２３ｇと２Ｍ塩酸を加え、３０℃で保持しながら良く撹拌した。
　この液を良く撹拌しながら１Ｍ水酸化ナトリウム水溶液をｐＨが６となるようゆっくり滴下し、オイルコア－シリカシェル粒子分散液を得た。得られたオイルコア－シリカシェル粒子分散液を保持し、熟成させた。 "First stage shell formation"
To 1300 g of the obtained aged emulsion, 23 g of a diluted sodium silicate aqueous solution (SiO 2 concentration 10.4% by mass, Na 2 O concentration 3.6% by mass) and 2M hydrochloric acid were added so that the pH was 2. The mixture was stirred well while being maintained at ℃.
While thoroughly stirring this liquid, a 1M aqueous sodium hydroxide solution was slowly added dropwise to adjust the pH to 6 to obtain an oil core-silica shell particle dispersion. The obtained oil core-silica shell particle dispersion was held and aged.
「２段目シェル形成」
　１段目シェル形成で得られたオイルコア－シリカシェル粒子分散液全量を７０℃に加熱し、撹拌しながら１Ｍ　ＮａＯＨをゆっくり添加し、ｐＨを９とした。
　次に、希釈したケイ酸ナトリウム水溶液（ＳｉＯ２濃度１０．４質量％、Ｎａ２Ｏ濃度３．６質量％）３３０ｇを、ｐＨ９になるように０．５Ｍ塩酸とともに徐々に添加した。
　この懸濁液を８０℃で１日間保持した後、室温まで冷却し、中空シリカ前駆体分散液を得た。 "Second stage shell formation"
The entire amount of the oil core-silica shell particle dispersion obtained in the first stage shell formation was heated to 70° C., and 1M NaOH was slowly added while stirring to adjust the pH to 9.
Next, 330 g of a diluted aqueous sodium silicate solution (SiO 2 concentration 10.4% by mass, Na 2 O concentration 3.6% by mass) was gradually added together with 0.5M hydrochloric acid so as to have a pH of 9.
This suspension was maintained at 80° C. for one day and then cooled to room temperature to obtain a hollow silica precursor dispersion.
「ろ過、洗浄、乾燥、焼成」
　中空シリカ前駆体分散液全量を、２Ｍ塩酸でｐＨ２まで中和後、定量ろ紙５Ｃを用いてろ過を行った。その後、８０℃のイオン交換水３５０ｍｌを加えて再度加圧濾過し、中空シリカケーキを洗浄した。
　ろ過後のケーキを、窒素雰囲気下で、１００℃で１時間、続けて４００℃で２時間乾燥し（昇温時間１０℃／ｍｉｎ）、有機成分を除去することで中空シリカ前駆体を得た。
　得られた中空シリカ前駆体を、１０００℃で１時間焼成（昇温時間１０℃／ｍｉｎ）することでシェルの焼き締めを行い、中空シリカ焼成粒子を得た。 "Filtration, washing, drying, firing"
The entire amount of the hollow silica precursor dispersion was neutralized to pH 2 with 2M hydrochloric acid, and then filtered using quantitative filter paper 5C. Thereafter, 350 ml of ion-exchanged water at 80°C was added and filtered under pressure again to wash the hollow silica cake.
The cake after filtration was dried in a nitrogen atmosphere at 100°C for 1 hour and then at 400°C for 2 hours (heating time 10°C/min) to remove organic components to obtain a hollow silica precursor. .
The obtained hollow silica precursor was baked at 1000° C. for 1 hour (heating time: 10° C./min) to harden the shell and obtain hollow baked silica particles.
「溶媒への分散」
　得られた中空シリカ焼成粒子１０ｇと、メチルエチルケトン（ＭＥＫ）２００ｍｌを２５０ｍｌのポリビンに入れ（中空シリカ焼成粒子７体積％、ＭＥＫ９３体積％）、ミックスローターを用いて３０ｒｐｍで２時間攪拌した。得られた混合液を、湿式微粒子化装置（スギノマシン株式会社製のスターバーストミニ、型式番号：ＨＪＰ－２５００１）にて、φ０．１ｍｍのノズルから加圧圧力５０ＭＰａにて噴出させる操作を３回繰り返した。得られたスラリーを、目開き１０μｍの電鋳ふるいに通し、固形分６．２質量％のシリカ粒子分散液を得た。 "Dispersion in solvent"
10 g of the obtained fired fired hollow silica particles and 200 ml of methyl ethyl ketone (MEK) were placed in a 250 ml polybottle (7% by volume of fired fired hollow silica particles, 93% by volume of MEK), and stirred at 30 rpm for 2 hours using a mix rotor. The obtained mixed liquid was spouted three times at a pressure of 50 MPa from a φ0.1 mm nozzle using a wet atomization device (Starburst Mini manufactured by Sugino Machine Co., Ltd., model number: HJP-25001). repeated. The obtained slurry was passed through an electroforming sieve with an opening of 10 μm to obtain a silica particle dispersion having a solid content of 6.2% by mass.
（例２）
　ＥＯ－ＰＯ－ＥＯブロックコポリマー（ＡＤＥＫＡ社製「プルロニックＦ６８」）の添加量を２ｇに、ソルビタン酸モノオレート（三洋化成社製イオネットＳ－８０）の添加量を２ｇに変更して中空シリカ粒子を作製したこと以外は例１と同じ条件で実施した。 (Example 2)
Hollow silica particles were prepared by changing the amount of EO-PO-EO block copolymer (“Pluronic F68” manufactured by ADEKA) to 2 g and the amount of sorbitan acid monooleate (Ionet S-80 manufactured by Sanyo Chemical Co., Ltd.) to 2 g. The experiment was carried out under the same conditions as in Example 1 except for the above.
（例３）
　ＥＯ－ＰＯ－ＥＯブロックコポリマー（ＡＤＥＫＡ社製「プルロニックＦ６８」）の添加量を１０ｇに変更し、ソルビタン酸モノオレート（三洋化成社製イオネットＳ－８０）を使用せず、圧力１００ｂａｒで乳化を行って中空シリカ粒子を作製したこと、スラリーを目開き１５μｍの電鋳ふるいに通したこと以外は例１と同じ条件で実施した。 (Example 3)
The amount of EO-PO-EO block copolymer ("Pluronic F68" manufactured by ADEKA Corporation) was changed to 10 g, and emulsification was performed at a pressure of 100 bar without using sorbitan acid monooleate (Ionet S-80 manufactured by Sanyo Chemical Co., Ltd.). The test was carried out under the same conditions as in Example 1, except that hollow silica particles were prepared and the slurry was passed through an electroforming sieve with an opening of 15 μm.
（例４）
　得られた中空シリカ前駆体を、１１００℃で１時間焼成（昇温時間１０℃／ｍｉｎ）して中空シリカ粒子を作製したこと、スラリーを目開き１５μｍの電鋳ふるいに通したこと以外は例１と同じ条件で実施した。 (Example 4)
Example except that the obtained hollow silica precursor was baked at 1100°C for 1 hour (heating time 10°C/min) to produce hollow silica particles, and the slurry was passed through an electroforming sieve with an opening of 15 μm. It was carried out under the same conditions as 1.
（例５）
　得られた中空シリカ前駆体を、８００℃で１時間焼成（昇温時間１０℃／ｍｉｎ）して中空シリカ粒子を作製したこと以外は例１と同じ条件で実施した。 (Example 5)
The process was carried out under the same conditions as in Example 1, except that the obtained hollow silica precursor was fired at 800° C. for 1 hour (heating time: 10° C./min) to produce hollow silica particles.
（例６）
　得られた中空シリカ前駆体を、７００℃で１時間焼成（昇温時間１０℃／ｍｉｎ）して中空シリカ粒子を作製したこと以外は例１と同じ条件で実施した。 (Example 6)
The process was carried out under the same conditions as in Example 1, except that the obtained hollow silica precursor was fired at 700° C. for 1 hour (heating time: 10° C./min) to produce hollow silica particles.
（例７）
　中空シリカ前駆体のろ過及び洗浄において、イオン交換水の代わりに水道水３５０ｍｌを用いたこと以外は、例１と同じ条件で実施した。 (Example 7)
Filtration and washing of the hollow silica precursor were carried out under the same conditions as in Example 1, except that 350 ml of tap water was used instead of ion-exchanged water.
（例８）
　例１と同様にして得られた中空シリカ焼成粒子１０ｇと、メチルエチルケトン（ＭＥＫ）２００ｍｌ、ＫＢＭ－５０３　０．１０ｇ（３－メタクリロキシプロピルトリメトキシシラン、信越化学工業社製）を２５０ｍｌのポリビンに入れ、ミックスローターを用いて３０ｒｐｍで２時間攪拌した。得られた混合液を、８０℃で１時間加熱した後、冷却し、湿式微粒子化装置（スギノマシン株式会社製のスターバーストミニ、型式番号：ＨＪＰ－２５００１）にて、φ０．１ｍｍのノズルから加圧圧力５０ＭＰａにて噴出させる操作を３回繰り返した。得られたスラリーを、目開き１０μｍの電鋳ふるいに通し、固形分６．２質量％のシリカ粒子分散液を得た。 (Example 8)
10 g of hollow fired silica particles obtained in the same manner as in Example 1, 200 ml of methyl ethyl ketone (MEK), and 0.10 g of KBM-503 (3-methacryloxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.) were placed in a 250 ml polybottle. The mixture was stirred for 2 hours at 30 rpm using a mix rotor. The resulting mixed solution was heated at 80°C for 1 hour, cooled, and atomized using a wet atomization device (Starburst Mini manufactured by Sugino Machine Co., Ltd., model number: HJP-25001) through a φ0.1 mm nozzle. The operation of ejecting at a pressurizing pressure of 50 MPa was repeated three times. The obtained slurry was passed through an electroforming sieve with an opening of 10 μm to obtain a silica particle dispersion having a solid content of 6.2% by mass.
（例９）
　例１と同様にして得られた中空シリカ焼成粒子１０ｇと、メチルエチルケトン（ＭＥＫ）２００ｍｌ、ＢＹＫ（登録商標）－Ｒ６０６　０．０２０ｇ（ポリヒドロキシカルボン酸エステル、ビッグケミー社製）を２５０ｍｌのポリビンに入れ、ミックスローターを用いて３０ｒｐｍで２時間攪拌した。得られた混合液を、８湿式微粒子化装置（スギノマシン株式会社製のスターバーストミニ、型式番号：ＨＪＰ－２５００１）にて、φ０．１ｍｍのノズルから加圧圧力５０ＭＰａにて噴出させる操作を３回繰り返した。得られたスラリーを、目開き１０μｍの電鋳ふるいに通し、固形分６．２質量％のシリカ粒子分散液を得た。 (Example 9)
10 g of hollow fired silica particles obtained in the same manner as in Example 1, 200 ml of methyl ethyl ketone (MEK), and 0.020 g of BYK (registered trademark)-R606 (polyhydroxycarboxylic acid ester, manufactured by Big Chemie) were placed in a 250 ml polybottle. The mixture was stirred for 2 hours at 30 rpm using a mix rotor. The obtained mixed liquid was spouted at a pressure of 50 MPa from a φ0.1 mm nozzle using an 8 wet atomization device (Starburst Mini manufactured by Sugino Machine Co., Ltd., model number: HJP-25001) for 3 times. Repeated times. The obtained slurry was passed through an electroforming sieve with an opening of 10 μm to obtain a silica particle dispersion having a solid content of 6.2% by mass.
（例１０）
　例８において、ＫＢＭ－５０３をＫＢＭ－１０３　０．１０ｇ（トリメトキシフェニルシラン、信越化学工業社製）に変更した以外は、例８と同様にして、シリカ粒子分散液を得た。 (Example 10)
A silica particle dispersion was obtained in the same manner as in Example 8, except that 0.10 g of KBM-103 (trimethoxyphenylsilane, manufactured by Shin-Etsu Chemical Co., Ltd.) was used instead of KBM-503.
（例１１）
　例１において、中空シリカ焼成粒子に代えて、ＳＯ－Ｃ２（メジアン径０．５μｍの爆燃法シリカ、中実シリカ、アドマテックス社製）を用い、スラリーを目開き３０μｍの電鋳ふるいに通した以外は、例１と同じ条件で実施した。 (Example 11)
In Example 1, SO-C2 (deflagration method silica with a median diameter of 0.5 μm, solid silica, manufactured by Admatex) was used instead of the hollow fired silica particles, and the slurry was passed through an electroformed sieve with an opening of 30 μm. Except for this, the experiment was carried out under the same conditions as in Example 1.
（例１２）
　例１において、中空シリカ焼成粒子に代えて、ｉＭ１６Ｋ（メジアン径１８μｍのガラスバルーン、３Ｍ社）を用い、スラリーを目開き３０μｍの電鋳ふるいに通した以外は、例１と同じ条件で実施した。 (Example 12)
In Example 1, the procedure was carried out under the same conditions as in Example 1, except that iM16K (glass balloon with a median diameter of 18 μm, manufactured by 3M Company) was used instead of the hollow fired silica particles, and the slurry was passed through an electroformed sieve with an opening of 30 μm. .
（例１３）
　例１で得られた中空シリカ焼成粒子１０ｇをそのまま使用した。 (Example 13)
10 g of hollow fired silica particles obtained in Example 1 were used as they were.
　なお、上記の各例で作製した中空シリカ粒子について、平均粒子径（Ｄ５０）、Ａｒ密度、Ｈｅ密度、比表面積、真球度及び５０体積％分散液の粘度を以下により測定した結果を表１に示す。 For the hollow silica particles produced in each of the above examples, the average particle diameter (D50), Ar density, He density, specific surface area, sphericity, and viscosity of a 50% by volume dispersion were measured as shown in Table 1. Shown below.
１．平均粒子径（Ｄ５０）
　中空シリカ粒子（二次粒子）をマイクロトラック・ベル社製の回折散乱式粒子径分布測定装置（ＭＴ３３００）によって測定し、粒子径分布（直径）の中央値（メジアン径、Ｄ５０）を測定した。測定は２回行い、平均値を求めた。 1. Average particle diameter (D50)
Hollow silica particles (secondary particles) were measured using a diffraction scattering particle size distribution analyzer (MT3300) manufactured by Microtrac Bell Co., Ltd., and the median value (median diameter, D50) of the particle size distribution (diameter) was measured. The measurement was performed twice and the average value was determined.
２．乾式ピクノメーターを用いた密度測定
　乾式ピクノメーター（Ｍｉｃｒｏｍｅｒｉｔｉｃｓ社製ＡｃｃｕＰｙｃＩＩ　１３４０）を用いて中空シリカ粒子の密度を測定した。測定条件は下記の通りである。
・試料セル：１０ｃｍ３セル
・試料重量：１．０ｇ
・測定ガス：ヘリウム、あるいは、アルゴン
・パージ回数：１０回
・パージ処理充填圧力：１３５ｋＰａｇ
・サイクル回数：１０回
・サイクル充填圧力：１３５ｋＰａｇ
・圧力平衡を終了するレート：０．０５ｋＰａｇ／分 2. Density measurement using a dry pycnometer The density of hollow silica particles was measured using a dry pycnometer (AccuPycII 1340 manufactured by Micromeritics). The measurement conditions are as follows.
・Sample cell: 10cm 3 cells ・Sample weight: 1.0g
・Measurement gas: Helium or argon ・Number of purges: 10 times ・Purge processing filling pressure: 135kPag
・Number of cycles: 10 times ・Cycle filling pressure: 135kPag
・Rate to finish pressure equilibrium: 0.05kPag/min
３．比表面積
　中空シリカ粒子を２３０℃で減圧乾燥して水分を完全に除去し、試料とした。この試料について、マイクロメリティック社製の自動比表面積、細孔分布測定装置「トライスターＩＩ」にて、窒素ガスを用いて多点ＢＥＴ法比表面積測定した。 3. Specific Surface Area Hollow silica particles were dried under reduced pressure at 230°C to completely remove moisture and used as samples. The specific surface area of this sample was measured using a multi-point BET method using nitrogen gas using an automatic specific surface area and pore distribution measuring device "Tristar II" manufactured by Micromeritic.
４．真球度
　日立ハイテク社製のＳ４８００を用いて、加速電圧５ｋＶで観察した中空シリカ粒子の走査型電子顕微鏡像（ＳＥＭ像）を得て、ＳＥＭ像から任意の１００個の粒子について、それぞれの外接円の径（ＤＬ）と、内接円の径（ＤＳ）とを測定し、外接円の径（ＤＬ）に対する内接円の径（ＤＳ）の比（ＤＳ／ＤＬ）を算出した平均値から真球度を求めた。 4. Sphericity Obtain a scanning electron microscope image (SEM image) of hollow silica particles observed at an accelerating voltage of 5 kV using S4800 manufactured by Hitachi High-Technology, and from the SEM image, determine the circumference of each of the 100 arbitrary particles. The diameter of the circle (DL) and the diameter of the inscribed circle (DS) are measured, and the ratio of the diameter of the inscribed circle (DS) to the diameter of the circumscribed circle (DL) is calculated from the average value. The sphericity was determined.
５．シリカ粒子分散液の粘度
　中空シリカ粒子の固形分濃度を５０体積％としたシリカ粒子分散液の粘度を以下により測定した。
　中空シリカ粒子の１００ｍｌとメチルエチルケトン（ＭＥＫ）１００ｍｌを２５０ｍｌのポリビンに入れ、ミックスローターで３０ｒｐｍ、２時間攪拌した。ただし中空シリカ粒子の１００ｍｌは、中空シリカ焼成粒子の密度ｄ（ｇ／ｃｍ３）から求めた質量１００×ｄ（ｇ）により調製した。得られた混合液を、湿式微粒子化装置（スギノマシン株式会社製のスターバーストミニ、型式番号：ＨＪＰ－２５００１）にて、φ０．１ｍｍのノズルから加圧圧力５０ＭＰａにて噴出させる操作を３回繰り返した。得られたスラリーを２５℃に調整し、その粘度を、回転式レオメータ（例えば、アントンパール（Ａｎｔｏｎ　ｐａａｒ）社製、モジュラーレオメーター　ＰｈｙｓｉｃａＭＣＲ－３０１）でせん断速度１ｒｐｍで３０秒測定し、得られた３０秒時点での粘度を求めた。 5. Viscosity of Silica Particle Dispersion The viscosity of a silica particle dispersion in which the solid content concentration of hollow silica particles was 50% by volume was measured as follows.
100 ml of hollow silica particles and 100 ml of methyl ethyl ketone (MEK) were placed in a 250 ml polybottle, and stirred with a mix rotor at 30 rpm for 2 hours. However, 100 ml of hollow silica particles was prepared using a mass of 100 x d (g) determined from the density d (g/cm 3 ) of the hollow fired silica particles. The obtained mixed liquid was spouted three times at a pressure of 50 MPa from a φ0.1 mm nozzle using a wet atomization device (Starburst Mini manufactured by Sugino Machine Co., Ltd., model number: HJP-25001). repeated. The resulting slurry was adjusted to 25° C., and its viscosity was measured using a rotary rheometer (for example, Modular Rheometer PhysicaMCR-301 manufactured by Anton Paar) at a shear rate of 1 rpm for 30 seconds. The viscosity at 30 seconds was determined.
＜試験例２＞
（評価サンプルＡ（樹脂フィルム）の作製）
　例１～１２のシリカ粒子分散液及び例１３の中空シリカ粒子を用いて樹脂フィルムを作製した。
　ビフェニル型エポキシ樹脂（エポキシ当量２７６、日本化薬（株）製「ＮＣ－３０００」）２５質量部をメチルエチルケトン（ＭＥＫ）１３質量部に攪拌しながら加熱溶解させた。室温にまで冷却後、そこへ活性エステル系硬化剤（ＤＩＣ（株）製「ＨＰ８０００－６５Ｔ」、活性基当量２２３、不揮発成分６５質量％のトルエン溶液）３２質量部を混合し、泡取り練太郎を用いて２０００ｒｐｍで５分間混練し、硬化促進剤として４－ジメチルアミノピリジン（ＤＭＡＰ）０．９質量部、２－エチル－４－メチルイミダゾール（四国化成工業株式会社製「２Ｅ４ＭＺ」）１．６質量部を混合し、ホモディスパーを用いて２０００ｒｐｍで５分間混合した。そこへアルゴンガスを用いた乾式ピクノメーターによる密度測定により求めた粒子の密度をＡ（ｇ／ｃｍ３）として、（３０×Ａ／２．２）質量部の粒子粉末となるよう、シリカ粒子分散液又は中空シリカ粒子を秤量して混合し、ホモディスパーを用いて２０００ｒｐｍで５分間混合した。 <Test Example 2>
(Preparation of evaluation sample A (resin film))
Resin films were produced using the silica particle dispersions of Examples 1 to 12 and the hollow silica particles of Example 13.
25 parts by mass of a biphenyl-type epoxy resin (epoxy equivalent: 276, "NC-3000" manufactured by Nippon Kayaku Co., Ltd.) was dissolved in 13 parts by mass of methyl ethyl ketone (MEK) while stirring and heating. After cooling to room temperature, 32 parts by mass of an active ester curing agent ("HP8000-65T" manufactured by DIC Corporation, active group equivalent: 223, toluene solution containing 65% by mass of non-volatile components) was mixed therein, and a foam removing agent was added. Kneaded at 2000 rpm for 5 minutes using a curing accelerator, 0.9 parts by mass of 4-dimethylaminopyridine (DMAP) and 1.6 parts of 2-ethyl-4-methylimidazole ("2E4MZ" manufactured by Shikoku Kasei Kogyo Co., Ltd.). Parts by mass were mixed and mixed for 5 minutes at 2000 rpm using a homodisper. Then, the silica particles were dispersed so that the density of the particles determined by density measurement using a dry pycnometer using argon gas was A (g/cm 3 ), and the particle powder was (30×A/2.2) parts by mass. The liquid or hollow silica particles were weighed and mixed, and mixed using a homodisper at 2000 rpm for 5 minutes.
　次に、離型処理された透明なポリエチレンテレフタレート（ＰＥＴ）フィルム（リンテック社製「ＰＥＴ５０１１　５５０」、厚み５０μｍ）を用意した。このＰＥＴフィルムの離型処理面に、アプリケーターを用いて、得られたワニスを乾燥後の厚みが４０μｍとなるように塗工し、１００℃のギアオーブン内で１０分間乾燥したあと裁断し、縦２００ｍｍ×横２００ｍｍ×厚み４０μｍの樹脂フィルムの未硬化物（Ｂステージフィルム）を備えた未硬化積層フィルムを作製した。
　得られた未硬化積層フィルムを、１９０℃に設定したギアオーブン内で９０分加熱して樹脂フィルムの未硬化物を硬化させて、硬化フィルムを作製した。 Next, a release-treated transparent polyethylene terephthalate (PET) film ("PET5011 550" manufactured by Lintec Corporation, thickness 50 μm) was prepared. The resulting varnish was applied to the release-treated surface of this PET film using an applicator so that the thickness after drying would be 40 μm, dried in a gear oven at 100°C for 10 minutes, and then cut lengthwise. An uncured laminated film including an uncured resin film (B stage film) measuring 200 mm x width 200 mm x thickness 40 μm was produced.
The obtained uncured laminated film was heated in a gear oven set at 190° C. for 90 minutes to harden the uncured resin film, thereby producing a cured film.
（評価サンプルＢ（積層体）の作製）
（１）ラミネート工程
　片面粗化銅箔（Ｆ０－ＷＳ、厚み１８μｍ、表面粗さＲｚ＝１．２μｍ、古河電気工業社製）を用意した。この銅箔に、名機製作所社製「バッチ式真空ラミネーターＭＶＬＰ－５００－ＩＩＡ」を用いて、上記で作製した未硬化積層フィルムを、未硬化樹脂フィルム（Ｂステージフィルム）の表面が銅箔粗化面に対向するようにラミネートして、銅箔／Ｂステージフィルム／ＰＥＴフィルムからなる積層構造体を得た。ラミネートの条件は、３０秒減圧して気圧を１３ｈＰａ以下とし、その後３０秒間、１００℃及び圧力０．８ＭＰａでプレスする条件とした。
（２）フィルム剥離工程
　積層構造体のＰＥＴフィルムを剥離した。
（３）硬化工程
　内部の温度が１８０℃のギアオーブン内に積層板を３０分間入れ、Ｂステージフィルムを硬化させて、絶縁層を形成した。 (Preparation of evaluation sample B (laminate))
(1) Lamination process A single-sided roughened copper foil (F0-WS, thickness 18 μm, surface roughness Rz=1.2 μm, manufactured by Furukawa Electric Co., Ltd.) was prepared. The uncured laminated film produced above was placed on this copper foil using a "batch type vacuum laminator MVLP-500-IIA" manufactured by Meiki Seisakusho Co., Ltd., so that the surface of the uncured resin film (B stage film) was rough with the copper foil. The film was laminated so as to face each other to obtain a laminated structure consisting of copper foil/B stage film/PET film. The lamination conditions were that the pressure was reduced to 13 hPa or less by reducing the pressure for 30 seconds, and then pressing was performed for 30 seconds at 100° C. and a pressure of 0.8 MPa.
(2) Film peeling step The PET film of the laminated structure was peeled off.
(3) Curing process The laminate was placed in a gear oven with an internal temperature of 180° C. for 30 minutes to cure the B-stage film and form an insulating layer.
（評価）
１．剥離強度の測定
　評価サンプルＢについて、銅箔側に１ｃｍ幅となるように短冊状に切込みを入れた。９０°剥離試験機に基板をセットし、つかみ具で切込みの入った銅めっきの端部をつまみあげ、銅めっきを２０ｍｍ剥離してピール強度（Ｎ／ｃｍ）を測定した。 (evaluation)
1. Measurement of Peel Strength Regarding evaluation sample B, a strip-shaped cut with a width of 1 cm was made on the copper foil side. The substrate was set in a 90° peel tester, the cut edge of the copper plating was picked up with a grip, 20 mm of the copper plating was peeled off, and the peel strength (N/cm) was measured.
２．塗膜の粒立ち
　前記未硬化積層フィルムの外観を観察し、塗膜の粒立ちを評価した。評価基準は以下の通りである。なお、Ａ、Ｂ評価を実用可能と判断した。
〔評価基準〕
　Ａ（良）：粒立ちなし。
　Ｂ（可）：塗工後に微細な凹凸が見られた。
　Ｃ（不可）：塗工時に粗大粒子が付着することによるスジ引きが見られた。 2. Graininess of coating film The appearance of the uncured laminated film was observed and graininess of the coating film was evaluated. The evaluation criteria are as follows. Note that the A and B evaluations were judged to be practical.
〔Evaluation criteria〕
A (Good): No graininess.
B (Acceptable): Fine irregularities were observed after coating.
C (unacceptable): Streaks due to adhesion of coarse particles were observed during coating.
　上記の試験結果を表１に合わせて示す。 The above test results are also shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１より、例１～１０は例１１、１３に比べて剥離強度が高く、接着力が強いことがわかった。また、例１～１０は塗膜の粒立ちも良好であり、いずれも実用に適したものであった。
　これに対し、例１１、１３は剥離強度が低く、塗膜の粒立ちも見られた。そして、例１２は塗工し乾燥したところ。塗膜が手で触れると剥がれる状態であり、顕微鏡で観察したところ、粒子が割れて破片状となっていた。このため、それ以上の評価は不可能であった。 From Table 1, it was found that Examples 1 to 10 had higher peel strength and stronger adhesive strength than Examples 11 and 13. Furthermore, in Examples 1 to 10, the graininess of the coating film was good, and all of them were suitable for practical use.
On the other hand, in Examples 11 and 13, the peel strength was low and graininess of the coating film was also observed. In Example 12, it was coated and dried. The paint film peeled off when touched, and when observed under a microscope, the particles were broken into fragments. For this reason, further evaluation was not possible.
　本発明を詳細にまた特定の実施形態を参照して説明したが、本発明の精神と範囲を逸脱することなく様々な変更や修正を加えられることは当業者にとって明らかである。本出願は、２０２２年５月９日出願の日本特許出願（特願２０２２－０７７０９２）に基づくものであり、その内容はここに参照として取り込まれる。 Although the invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on a Japanese patent application (Japanese Patent Application No. 2022-077092) filed on May 9, 2022, the contents of which are incorporated herein by reference.

Claims (11)

  1. 　中空シリカ粒子と溶媒を含み、前記中空シリカ粒子の平均粒子径が０．２～１０μｍの範囲にあるシリカ粒子分散液。 A silica particle dispersion containing hollow silica particles and a solvent, wherein the average particle diameter of the hollow silica particles is in the range of 0.2 to 10 μm.
  2. 　前記中空シリカ粒子は、アルゴンガスを用いた乾式ピクノメーターによる密度測定により求めた粒子の密度が０．３５～２．００ｇ／ｃｍ３である、請求項１に記載のシリカ粒子分散液。 The silica particle dispersion according to claim 1, wherein the hollow silica particles have a particle density of 0.35 to 2.00 g/cm 3 as determined by density measurement with a dry pycnometer using argon gas.
  3. 　前記中空シリカ粒子は、ヘリウムガスを用いた乾式ピクノメーターによる密度測定により求めた粒子の密度が２．００～２．３０ｇ／ｃｍ３である、請求項１又は２に記載のシリカ粒子分散液。 The silica particle dispersion according to claim 1 or 2, wherein the hollow silica particles have a particle density of 2.00 to 2.30 g/cm 3 as determined by density measurement with a dry pycnometer using helium gas.
  4. 　前記中空シリカ粒子は、ＢＥＴ比表面積が１～１００ｍ２／ｇである、請求項１～３のいずれか１項に記載のシリカ粒子分散液。 The silica particle dispersion according to any one of claims 1 to 3, wherein the hollow silica particles have a BET specific surface area of 1 to 100 m 2 /g.
  5. 　前記中空シリカ粒子は、真球度が０．７５～１．０である、請求項１～４のいずれか１項に記載のシリカ粒子分散液。 The silica particle dispersion according to any one of claims 1 to 4, wherein the hollow silica particles have a sphericity of 0.75 to 1.0.
  6. 　さらに、ビニル基、フェニル基、フェニルアミノ基、炭素数４以上のアルキル基、メタクリル基及びエポキシ基からなる群から選択される少なくとも１つの基を有するシラン化合物を含有する、請求項１～５のいずれか１項に記載のシリカ粒子分散液。 Claims 1 to 5 further comprising a silane compound having at least one group selected from the group consisting of a vinyl group, a phenyl group, a phenylamino group, an alkyl group having 4 or more carbon atoms, a methacryl group, and an epoxy group. The silica particle dispersion according to any one of the items.
  7. 　さらに、有機揺変剤を含有する、請求項１～６のいずれか１項に記載のシリカ粒子分散液。 The silica particle dispersion according to any one of claims 1 to 6, further comprising an organic thixotropic agent.
  8. 　前記溶媒は、水、炭化水素類、アルコール類、酢酸エステル類、ケトン類、セロソルブ類、グリコールエーテル類、塩化炭化水素類及び極性溶媒からなる群から選択される少なくとも１種を含む、請求項１～７のいずれか１項に記載のシリカ粒子分散液。 Claim 1, wherein the solvent includes at least one selected from the group consisting of water, hydrocarbons, alcohols, acetic esters, ketones, cellosolves, glycol ethers, chlorinated hydrocarbons, and polar solvents. The silica particle dispersion according to any one of items 1 to 7.
  9. 　前記中空シリカ粒子の固形分濃度を５０体積％としたときの２５℃における前記シリカ粒子分散液の粘度が２０～２００００ｍＰａ・ｓである、請求項１～８のいずれか１項に記載のシリカ粒子分散液。 The silica particles according to any one of claims 1 to 8, wherein the viscosity of the silica particle dispersion at 25 ° C. is 20 to 20,000 mPa s when the solid content concentration of the hollow silica particles is 50% by volume. dispersion liquid.
  10. 　請求項１～９のいずれか１項に記載のシリカ粒子分散液を含む樹脂組成物。 A resin composition comprising the silica particle dispersion according to any one of claims 1 to 9.
  11. 　溶媒と平均粒子径が０．２～１０μｍの範囲の中空シリカ粒子の粉末とを混合し、混合液を分散処理し、分級して中空シリカ粒子の凝集物を除去する、シリカ粒子分散液の製造方法。 Production of a silica particle dispersion liquid by mixing a solvent and powder of hollow silica particles with an average particle size in the range of 0.2 to 10 μm, dispersing the mixed liquid, and classifying to remove aggregates of hollow silica particles. Method.
PCT/JP2023/016363 2022-05-09 2023-04-25 Silica particle dispersion liquid WO2023218948A1 (en)

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